1. An image processing apparatus, comprising: an acquisition unit configured to acquire a plurality of divided filters being configured such that a calculation result becomes a target filter to be applied to an input image; a filter processing unit configured to apply the plurality of divided filters to the input image to generate a plurality of intermediate images; and an addition unit configured to add the plurality of intermediate images while shifting positions of the respective intermediate images so that positions of the respective intermediate images correspond to a position of a focused pixel of the target filter to generate an output image, wherein the filter processing unit generates the intermediate images while changing an area to be used for performing calculation, for each of the plurality of divided filters.