An image processing apparatus includes an image sensor configured to output a plurality of images obtained by applying different gains in one exposure where a capacity of a charge accumulation portion for accumulating electric charges is common to all of the images, a first combining unit configured to acquire the plurality of images and perform combining by adjusting brightness of an image other than a darkest image with brightness of the darkest image among the plurality of images, a second combining unit configured to perform combining by adjusting brightness of an image other than a lightest image with brightness of a lightest image among the plurality of images, and a combining method selection unit configured to select the first or second combining unit.