1. An image quality evaluation system comprising: a difference calculator that calculates a difference between data representing a feature of a pixel group comprised of at least one pixel making up a first image, and data representing a feature of a pixel group comprised of at least one pixel making up a second image; a degree-of-focused-area calculator that sums up a number of the pixels decided to be a pixel of interest falling within a specific range in a color space, out of the pixels of said pixel group and a vicinal pixel group in a vicinity of said pixel group of at least one of said first and second images, and calculates a degree of focused area indicating the degree of being a focused area of said pixel group using a sum-up result; a difference weighting section that applies weighting to the difference in feature for said pixel group based on said degree of focused area; and an image quality value calculator that calculates an image quality value for said first image based on the difference weighted by said difference weighting section.