1. An image processing apparatus for processing a plurality of image data whose reading positions are displaced in a main scanning direction and a sub scanning direction upon reading a document, comprising: an inputting unit configured to input a target resolution; a super-resolution processing unit configured to execute super-resolution processing for respective positions using image data, corresponding to each position of the document in the sub scanning direction, of the plurality of image data; and a variable-magnification processing unit configured to further execute variable-magnification processing of the image data, which has undergone the super-resolution processing at that position, when the resolution of the image data executed super-resolution processing by said super-resolution processing unit is lower than the resolution input by said inputting unit.