In a picture enlarging processing employing a MAP method, the processing volume is to be decreased to obtain a clear picture without producing blocked distortion without deteriorating the picture quality from that in the conventional practice. An energy function of a picture varied in dependence upon the input picture is defined in advance and stored. An input picture is enlarged, that is the number of pixels is increased, and a value which decreases the energy in a pixel of the enlarged picture is calculated. This energy decreasing value is added to the pixel and the pixel value is updated to adjust the picture quality to raise the resolution. The pixel value is updated a number of times to adjust the picture quality to raise the resolution.