diff --git a/src/main/java/jp/sf/fess/helper/SystemHelper.java b/src/main/java/jp/sf/fess/helper/SystemHelper.java
index d256444a4..0e5ad8119 100644
--- a/src/main/java/jp/sf/fess/helper/SystemHelper.java
+++ b/src/main/java/jp/sf/fess/helper/SystemHelper.java
@@ -123,6 +123,8 @@ public class SystemHelper implements Serializable {
 
     public String idField = "id";
 
+    public String langField = "lang_s";
+
     @InitMethod
     public void init() {
         final File[] files = ResourceUtil.getJarFiles(launcherFileNamePrefix);
@@ -430,4 +432,24 @@ public class SystemHelper implements Serializable {
         return StringUtils.abbreviate(str, maxTextLength);
     }
 
+    public String normalizeLang(final String value) {
+        if (StringUtil.isBlank(value)) {
+            return null;
+        }
+
+        final StringBuilder buf = new StringBuilder(value.length());
+        for (int i = 0; i < value.length(); i++) {
+            final char c = value.charAt(i);
+            if ('a' <= c && c <= 'z') {
+                buf.append(c);
+            } else if (buf.length() > 0) {
+                break;
+            }
+        }
+        if (buf.length() > 0) {
+            return buf.toString();
+        }
+        return null;
+    }
+
 }
diff --git a/src/main/java/jp/sf/fess/transformer/FessXpathTransformer.java b/src/main/java/jp/sf/fess/transformer/FessXpathTransformer.java
index 1e792e249..794380d95 100644
--- a/src/main/java/jp/sf/fess/transformer/FessXpathTransformer.java
+++ b/src/main/java/jp/sf/fess/transformer/FessXpathTransformer.java
@@ -80,6 +80,8 @@ public class FessXpathTransformer extends AbstractFessXpathTransformer {
 
     public String contentXpath = "//BODY";
 
+    public String langXpath = "//HTML/@lang";
+
     public String digestXpath = "//META[@name='description']/@content";
 
     public String canonicalXpath = "//LINK[@rel='canonical']/@href";
@@ -245,6 +247,12 @@ public class FessXpathTransformer extends AbstractFessXpathTransformer {
             putResultDataBody(dataMap, systemHelper.expiresField,
                     FessFunctions.formatDate(documentExpires));
         }
+        // lang
+        final String lang = systemHelper.normalizeLang(getSingleNodeValue(
+                document, langXpath, true));
+        if (lang != null) {
+            putResultDataBody(dataMap, systemHelper.langField, lang);
+        }
         // title
         // content
         putResultDataBody(dataMap, "content",
diff --git a/src/test/java/jp/sf/fess/helper/SystemHelperTest.java b/src/test/java/jp/sf/fess/helper/SystemHelperTest.java
index 6a1669cd5..f9b0056d6 100644
--- a/src/test/java/jp/sf/fess/helper/SystemHelperTest.java
+++ b/src/test/java/jp/sf/fess/helper/SystemHelperTest.java
@@ -40,4 +40,30 @@ public class SystemHelperTest extends S2TestCase {
         path = "[]^$.*+?,{}|%\\";
         assertEquals(path, systemHelper.encodeUrlFilter(path));
     }
+
+    public void test_normalizeLang() {
+        String value = null;
+        assertNull(systemHelper.normalizeLang(value));
+
+        value = "";
+        assertNull(systemHelper.normalizeLang(value));
+
+        value = "ja";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+
+        value = " ja ";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+
+        value = "_ja";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+
+        value = "ja-JP";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+
+        value = "ja_JP";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+
+        value = "ja_JP_AAA";
+        assertEquals("ja", systemHelper.normalizeLang(value));
+    }
 }