diff --git a/app/controllers/fluentd/settings_controller.rb b/app/controllers/fluentd/settings_controller.rb
index dd45c9f..6ac3a1b 100644
--- a/app/controllers/fluentd/settings_controller.rb
+++ b/app/controllers/fluentd/settings_controller.rb
@@ -65,8 +65,9 @@ class Fluentd::SettingsController < ApplicationController
   private
 
   def setting_params
+    setting_params = params.require(:setting).permit(:path, :format, :regexp, *Fluentd::Setting::InTail.known_formats, :tag, :rotate_wait, :pos_file, :read_from_head, :refresh_interval)
     {
       :pos_file => "/tmp/fluentd-#{@fluentd.id}-#{Time.now.to_i}.pos",
-    }.merge params.require(:setting).permit(:path, :format, *Fluentd::Setting::InTail.known_formats, :tag, :rotate_wait, :pos_file, :read_from_head, :refresh_interval)
+    }.merge setting_params
   end
 end
diff --git a/app/models/fluentd/setting.rb b/app/models/fluentd/setting.rb
index 0c1b718..083489f 100644
--- a/app/models/fluentd/setting.rb
+++ b/app/models/fluentd/setting.rb
@@ -2,7 +2,7 @@ class Fluentd
   module Setting
     class InTail
       include ActiveModel::Model
-      attr_accessor :path, :tag, :format, :time_format, :rotate_wait, :pos_file, :read_from_head, :refresh_interval
+      attr_accessor :path, :tag, :format, :regexp, :time_format, :rotate_wait, :pos_file, :read_from_head, :refresh_interval
 
       validates :path, presence: true
       validates :tag, presence: true
@@ -10,7 +10,6 @@ class Fluentd
 
       def self.known_formats
         {
-          :regexp => [],
           :apache2 => [:time_format],
           :nginx => [:time_format],
           :syslog => [:time_format],
@@ -18,6 +17,7 @@ class Fluentd
           :csv => [:keys, :time_key],
           :ltsv => [:delimiter, :time_key],
           :json => [:time_key],
+          :grok => [:grok_str],
         }
       end
       attr_accessor *known_formats.values.flatten.compact
@@ -43,21 +43,51 @@ class Fluentd
         when %r|/var/log|
           :syslog
         else
-          :regexp
+          :grok
+        end
+      end
+
+      def extra_format_options
+        self.class.known_formats[format.to_sym] || []
+      end
+
+      def format_specific_conf
+        return "" if %w(grok regexp).include?(format)
+
+        indent = " " * 2
+        format_specific_conf = ""
+        extra_format_options.each do |key|
+          format_specific_conf << "#{indent}#{key} #{send(key)}\n"
+        end
+        format_specific_conf
+      end
+
+      def certain_format_line
+        case format
+        when "grok"
+          "format #{grok_str} # grok: #{grok_str}" # TODO: convert to regexp
+        when "regexp"
+          "format #{regexp}"
+        else
+          "format #{format}"
         end
       end
 
       def to_conf
-        <<-XML.strip_heredoc.gsub(/^[ ]+\n/m, "")
-          <source>
-            type tail
-            path #{path}
-            tag #{tag}
-            #{read_from_head.to_i.zero? ? "" : "read_from_head true"}
-            #{pos_file.present? ? "pos_file #{pos_file}" : ""}
-            #{rotate_wait.present? ? "rotate_wait #{rotate_wait}" : ""}
-            #{refresh_interval.present? ? "refresh_interval #{refresh_interval}" : ""}
-          </source>
+        # NOTE: Using strip_heredoc makes more complex for format_specific_conf indent
+        <<-XML.gsub(/^[ ]*\n/m, "")
+<source>
+  type tail
+  path #{path}
+  tag #{tag}
+  #{certain_format_line}
+#{format_specific_conf}
+
+  #{read_from_head.to_i.zero? ? "" : "read_from_head true"}
+  #{pos_file.present? ? "pos_file #{pos_file}" : ""}
+  #{rotate_wait.present? ? "rotate_wait #{rotate_wait}" : ""}
+  #{refresh_interval.present? ? "refresh_interval #{refresh_interval}" : ""}
+</source>
         XML
       end
     end
diff --git a/app/views/fluentd/settings/_form.html.haml b/app/views/fluentd/settings/_form.html.haml
index da8dc68..8e1c488 100644
--- a/app/views/fluentd/settings/_form.html.haml
+++ b/app/views/fluentd/settings/_form.html.haml
@@ -10,11 +10,16 @@
   = f.label :format
   = f.hidden_field :format
   = f.text_field :format, class: "form-control", disabled: true
-- @setting.known_formats[@setting.format.to_sym].each do |key|
-  %label= key
-  = f.hidden_field key
-  = @setting.send(key)
-  %br
+- if @setting.known_formats[@setting.format.to_sym]
+  - @setting.known_formats[@setting.format.to_sym].each do |key|
+    %label= key
+    = f.hidden_field key
+    = @setting.send(key)
+    %br
+- else
+  %label= @setting.format
+  = f.hidden_field :regexp
+  = @setting.regexp
 %div.form-group
   = f.label :tag
   = f.text_field :tag, class: "form-control"
diff --git a/app/views/shared/vue/_in_tail_format.html.erb b/app/views/shared/vue/_in_tail_format.html.erb
index 02b4db9..a567098 100644
--- a/app/views/shared/vue/_in_tail_format.html.erb
+++ b/app/views/shared/vue/_in_tail_format.html.erb
@@ -1,13 +1,35 @@
 <div id="in_tail_format" class="form-group" formatOptions="<%= formats.to_json %>" initialSelected="<%= initialSelected %>">
   <div class="form-group">
-    <label>format(TODO: use Glok?)</label>
-    <select name="setting[format]" v-model="format" class="form-control">
-      <option v-repeat="formats" value="{{ $value }}" v-attr="selected: format==$value">{{ $value }}</option>
-    </select>
+    <label>
+      <input type="radio" v-model="formatType" value="bundled">bundled
+    </label>
+    <label>
+      <input type="radio" v-model="formatType" value="regexp">regexp
+    </label>
   </div>
-  <div class="form-group" v-repeat="options">
-    <label>{{ $value }} </label>
-    <input type="text" name="setting[{{ $value }}]" />
+
+  <div v-if="formatType == 'bundled'">
+    <div class="form-group">
+      <label>format</label>
+      <select name="setting[format]" v-model="format">
+        <option v-repeat="formats" value="{{ $value }}" v-attr="selected: format==$value">{{ $value }}</option>
+      </select>
+    </div>
+    <div class="form-group" v-repeat="options">
+      <label>{{ $value }} </label>
+      <input type="text" name="setting[{{ $value }}]" size="100%" />
+    </div>
+    <div v-if="format == 'grok'" class="well well-sm">
+      TODO: grok reference
+    </div>
+  </div>
+
+  <div v-if="formatType == 'regexp'">
+    <div class="form-group">
+      <label>regexp</label>
+      <input type="hidden" name="setting[format]" value="regexp" />
+      <input type="text" name="setting[regexp]" v-model="regexp" size="100%" />
+    </div>
   </div>
 
   <div class="well well-sm">