For a mosaic image in a repeated cycle with “I”דJ” (“I” and “J” are integers of 2 or more) pixels, a color mix ratio is stored in a memory unit by being associated with a pixel position in I×J pixels so that a color mix ratio A associated with a pixel position in I×J pixels of an object pixel for mixed color correction is read from the memory unit, and a mixed color component included in the object pixel is removed based on the color mix ratio A and a color signal of the object pixel to calculate a white balance gain based on a color signal of each of pixels in the mosaic image for which the mixed color correction is applied.