1. An image search device comprising: a storage unit configured to store an image of a photographic subject obtained by an imaging unit, in a form adapted to a database; and a processor coupled to a memory, the processor configure to execute computer-executable units comprising: a similarity search unit that performs a similarity search on the image of the photographic subject stored in the storage unit by using a query image; and a query image generation unit that generates a new query image by synthesizing a correct image used as a criteria with another correct image or synthesizing the correct image used as the criteria with a negative-positive inverted incorrect image, of a result of the search by the similarly search unit, wherein the similarity search unit performs the similarity search on the image of the photographic subject stored in the storage unit by using the new query image generated by the query image generation unit, and wherein the correct image, the another correct image, and the negative-positive inverted incorrect image are obtained from the storage unit as the result of the similarity search performed by the similarly search unit.