1. An image quality evaluation method comprising: calculating an alternating-current component differential value, which is a difference between a statistical quantity of alternating-current components within a pixel group in a first image and a statistical quantity of alternating-current components within a pixel group in a second image at the same position as a position of said pixel group in said first image, weighting-processing to said alternating-current component differential value based on at least high frequency components, block distortion or local degradation in said second image, and evaluating image quality of said second image based on said weighted alternating-current component differential value; wherein said statistical quantity of alternating-current components within the pixel group is an average of absolute differences within an image group, each of said differences being an absolute difference between an average of pixel values within said pixel group and each pixel value within said pixel group.