When executing super-resolution processing, both reduction in necessary memory capacity and generation of high-resolution image data having a desired image quality are achieved. This invention provides an image forming method in an image forming apparatus capable of executing super-resolution processing using a plurality of low-resolution image data to generate high-resolution image data. The method includes steps of acquiring a plurality of low-resolution image data, selecting image data to be deleted from the plurality of acquired image data on the basis of spatial frequency information or color information of each image data, deleting the selected image data, and storing, as image data used in the super-resolution processing, remaining image data which are not deleted among the plurality of image data.