A search request input processing unit holds an input query word in a query word holding unit. An associative word unfolding processing unit acquires associative words in association with the query word held in the query word holding unit with reference to an associative word dictionary. An image content search processing unit using associative words makes a keyword search of image information on the basis of the obtained associative words and the query word. A sensory pattern unfolding processing unit obtains the query word and sensory patterns corresponding to associative words of the query word, and searches image information using feature amounts of the obtained sensory patterns. A search result integration processing unit integrates the search results obtained by the image content word search processing unit and sensory pattern search processing unit.