1. An image processing apparatus comprising: a sensitivity difference correction processing unit that receives a photoelectric conversion signal and executes sensitivity difference correction processing, the photoelectric conversion signal being output by an image sensor based on incident light being incident through a color filter, wherein the sensitivity difference positive processing unit: acquires a pixel value of a color filter unit which has a same color as a correction target pixel and is present in surroundings of the correction target pixel; calculates an additional value by adding a difference between weighted mean pixel values “a” and “b” of two kinds of pixel groups “A” and “B” classified according to positions of the pixels to the pixel value of the correction target pixel, the weighted mean pixel values corresponding to distances of the pixel groups from the correction target pixel; and calculates a mean value of the pixel value of the correction target pixel and the additional value as a corrected pixel value of the correction target pixel.