An image search apparatus capable of communicating with an image scanning apparatus includes: a common area extraction portion to compare a plurality of registration images stored in the storage portion and to extract a common area including an identical or similar image among a plurality of registration images; a search area determination portion to determine a non-common area excluding the common area, as a search area; a transmission request portion to request transmission of a document image if, as a result of comparison by the comparison portion, a registration image in which the reference image is identical or similar to the partial image does not exist in the plurality of registration images; and a registration portion to, in response to a request by the transmission request portion, store a document image received from the image scanning apparatus as a registration image into the storage portion.