1. A similar image retrieval system comprising: a first image input unit configured to receive an input of a search target image; a first face detecting unit configured to detect a first face from the inputted search target image; a face feature value calculating unit configured to calculate a feature value of the detected first face; and a database recording unit configured to record the calculated face feature value; a second image input unit configured to receive an input of a key image for search; a second face detecting unit configured to detect a second face from the inputted key image; a face angle calculating unit configured to calculate a face angle of the detected second face; a combined pattern determining unit configured to determine a combined pattern by the calculated face angle; a combined face generating unit configured to generate a combined face image according to the determined combined pattern; and a second face feature value calculating unit configured to calculate a feature value of the second face using the generated combined face image; and a face feature value searching unit configured to repeat the combined face generating unit and the face feature value calculating unit according to a number of the determined combined patterns and search a database using a plurality of calculated face feature values as queries; and a search result integrating unit configured to integrate a plurality of retrieved search results.