An image processing apparatus that generates image data having a high dynamic range by combining a plurality of image data having different exposure amounts includes: an input unit configured to input a plurality of M-bit image data; a determining unit configured to determine reference image data serving as an exposure reference from among the plurality of input M-bit image data; a composition unit configured to combine the plurality of M-bit image data, and generate one N-bit composite image data (N>M); a characteristic parameter setting unit configured to set a characteristic parameter of tone compression on the N-bit composite image data such that a predetermined reference luminance in the reference image data does not change; and a generating unit configured to generate M-bit composite image data by compressing a luminance tone of an image component based on the set characteristic parameter.