An image searching system, an image searching method, and a medium storing an image searching program for improving search accuracy while reducing the user burden when searching for similar images based on a plurality of key images are disclosed.A plurality of feature quantity types is extracted from each of plural key images (S42), and feature quantities of the same type are compared between the key images to select those feature quantities having approximately equal values as the key image feature quantities to be used as search criteria (S43). Feature quantities in the target images are then extracted (S45) and a degree of similarity between the target image and key images is calculated based on a key image feature quantity and the same feature quantity in the target image (S46) Based on the resulting degree of similarity, target images having a high similarity to the key image are output as the search result (S47).