diff --git a/src/main/java/org/codelibs/fess/app/service/SearchService.java b/src/main/java/org/codelibs/fess/app/service/SearchService.java
index ea82910af..3bdb1df3f 100644
--- a/src/main/java/org/codelibs/fess/app/service/SearchService.java
+++ b/src/main/java/org/codelibs/fess/app/service/SearchService.java
@@ -61,6 +61,8 @@ import org.elasticsearch.index.query.BoolQueryBuilder;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.lastaflute.taglib.function.LaFunctions;
 import org.lastaflute.web.util.LaRequestUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class SearchService {
 
@@ -68,6 +70,8 @@ public class SearchService {
     //                                                                            Constant
     //
 
+    private static final Logger logger = LoggerFactory.getLogger(SearchService.class);
+
     // ===================================================================================
     //                                                                           Attribute
     //
@@ -117,6 +121,16 @@ public class SearchService {
                                     .similarDocHash(params.getSimilarDocHash()).responseFields(queryHelper.getResponseFields())
                                     .searchRequestType(params.getType()).build();
                         }, (searchRequestBuilder, execTime, searchResponse) -> {
+                            searchResponse.ifPresent(r -> {
+                                if (r.getTotalShards() != r.getSuccessfulShards() && fessConfig.isQueryTimeoutLogging()) {
+                                    // partial results
+                                    StringBuilder buf = new StringBuilder(1000);
+                                    buf.append("[SEARCH TIMEOUT] {\"exec_time\":").append(execTime)//
+                                            .append(",\"request\":").append(searchRequestBuilder.toString())//
+                                            .append(",\"response\":").append(r.toString()).append('}');
+                                    logger.warn(buf.toString());
+                                }
+                            });
                             final QueryResponseList queryResponseList = ComponentUtil.getQueryResponseList();
                             queryResponseList.init(searchResponse, pageStart, pageSize);
                             return queryResponseList;
diff --git a/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java b/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
index 018407fa5..4ca01bd24 100644
--- a/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
+++ b/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
@@ -564,6 +564,9 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
     /** The key of the configuration. e.g. 10000 */
     String QUERY_TIMEOUT = "query.timeout";
 
+    /** The key of the configuration. e.g. true */
+    String QUERY_TIMEOUT_LOGGING = "query.timeout.logging";
+
     /** The key of the configuration. e.g. location */
     String QUERY_GEO_FIELDS = "query.geo.fields";
 
@@ -2994,6 +2997,20 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
      */
     Integer getQueryTimeoutAsInteger();
 
+    /**
+     * Get the value for the key 'query.timeout.logging'. <br>
+     * The value is, e.g. true <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     */
+    String getQueryTimeoutLogging();
+
+    /**
+     * Is the property for the key 'query.timeout.logging' true? <br>
+     * The value is, e.g. true <br>
+     * @return The determination, true or false. (if not found, exception but basically no way)
+     */
+    boolean isQueryTimeoutLogging();
+
     /**
      * Get the value for the key 'query.geo.fields'. <br>
      * The value is, e.g. location <br>
@@ -6625,6 +6642,14 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             return getAsInteger(FessConfig.QUERY_TIMEOUT);
         }
 
+        public String getQueryTimeoutLogging() {
+            return get(FessConfig.QUERY_TIMEOUT_LOGGING);
+        }
+
+        public boolean isQueryTimeoutLogging() {
+            return is(FessConfig.QUERY_TIMEOUT_LOGGING);
+        }
+
         public String getQueryGeoFields() {
             return get(FessConfig.QUERY_GEO_FIELDS);
         }
@@ -8282,6 +8307,7 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             defaultMap.put(FessConfig.INDEX_INDICES_TIMEOUT, "1m");
             defaultMap.put(FessConfig.QUERY_MAX_LENGTH, "1000");
             defaultMap.put(FessConfig.QUERY_TIMEOUT, "10000");
+            defaultMap.put(FessConfig.QUERY_TIMEOUT_LOGGING, "true");
             defaultMap.put(FessConfig.QUERY_GEO_FIELDS, "location");
             defaultMap.put(FessConfig.QUERY_BROWSER_LANG_PARAMETER_NAME, "browser_lang");
             defaultMap.put(FessConfig.QUERY_REPLACE_TERM_WITH_PREFIX_QUERY, "true");
diff --git a/src/main/resources/fess_config.properties b/src/main/resources/fess_config.properties
index e6ff91ade..55dc0ec17 100644
--- a/src/main/resources/fess_config.properties
+++ b/src/main/resources/fess_config.properties
@@ -287,6 +287,7 @@ index.indices.timeout=1m
 # query
 query.max.length=1000
 query.timeout=10000
+query.timeout.logging=true
 query.geo.fields=location
 query.browser.lang.parameter.name=browser_lang
 query.replace.term.with.prefix.query=true