A first generation unit generates a RAW image reduced in the horizontal direction from a RAW image including pixels each having single-color signal information, by limiting the band of spatial frequencies in the horizontal direction and decreasing the number of pixels in the horizontal direction. The RAW image reduced in the horizontal direction is stored in a line memory. A second generation unit generates a reduced RAW image by decreasing, at least in the vertical direction, the number of pixels of the RAW image reduced in the horizontal direction. This makes it possible to generate a reduced RAW image using little memory capacity.