Image search device, image search method, and image search program

An image search device (2) is configured to comprise: a data acquisition unit (11) for acquiring image data items that respectively indicate a plurality of images captured by cameras (1-n) (n=1, ..., N) and identification data items that indicate the types of the cameras that have captured the respective images; and a common type specification unit (13) for, on the basis of the types of the cameras indicated by the identification data items acquired by the data acquisition unit (11), specifying types having a commonality in the types of feature amounts that can be extracted from the images. Further, the image search device (2) comprises: a feature amount extraction unit (14) for extracting, from the images indicated by the image data items acquired by the data acquisition unit (11), feature amounts for the types specified by the common type specification unit (13); and an image search unit (16) for, among the plurality of feature amounts extracted by the feature amount extraction unit (14), making a comparison between a feature amount extracted from a query image that is an image included in the plurality of images and a feature amount extracted from one or more gallery images that are included in the plurality of images and that are other than the query image, and for searching for a gallery image, in which the same subject as a subject included in the query image is included, on the basis of the result of comparison between the feature amounts.