This invention has as its object to detect an image area of interest in an image file by a method with a lighter processing load by making determination using characteristics of a quantization table.Since spatial frequency information, chromaticity information, and a quantization table are acquired for respective predetermined blocks from inputted compressed image data, and are used in combination upon searching the compression-recorded image data for an image of interest, information containing AC component information for each image data block is acquired without any advanced calculations, thus searching for the image of interest in the image file.