An object of the present invention is to provide an image restoration function which ensures physical accuracy, while reducing computational cost, by eliminating a division into local regions. The present invention provides an image processing apparatus including: an initial solution generating unit configured to generate an initial solution of a restored image and an initial solution of a transmittance distribution; and an iterative processing unit configured to receive input data on the generated initial solution of the restored image and input data on the generated initial solution of the transmittance distribution, and to repeat updating of one of the transmittance distribution and the restored image, using the transmittance distribution and the restored image, in such a way as to alternate the updating of the transmittance distribution with the updating of the restored image independently for each pixel.