To obtain more natural image quality in more simplified configuration when performing gradation conversion processing onto a PinP image.

A gradation conversion section 46 performs gradation conversion for converting a supplied PinP image of 12 bits, for example, into a PinP image of 8 bits. In a case where a pixel of interest is a pixel in a random dither region inside a predetermined region from a boundary of a master image and a slave image of the PinP image, a switch 82 selects a random noise output section 81. In a case where the pixel of interest is a pixel in any other region than the random dither region, on the other hand, the switch 82 selects a two-dimensional filter 80. Thus, in the case where the pixel of interest is the pixel in the random dither region, the gradation conversion section 46 performs gradation conversion according to a random dither method. In the case where the pixel of interest is the pixel in any other region than the random dither region, on the other hand, the gradation conversion section 46 performs gradation conversion according to an error diffusion method. The invention may be applicable to an image processing for processing a PinP image, for example.