A periodicity determining unit determines whether an image region including a target pixel is a periodic region in which pixel values vary periodically. A first generating unit generates a pixel value using a first interpolation method. A second generating unit generates a pixel value using a second interpolation method. A control unit determines, based on the determination result of the periodicity determining unit, which one of the first and second generating units is to be used for generating a pixel value of the target pixel. A pixel value inserting unit inserts the generated pixel value to the target pixel. The periodicity determining unit includes a cycle estimating unit to estimate, using pixel values of pixels within the image region, a variation cycle of the pixel values, and/or a determining unit to determine whether each region positioned at left and right sides of the target pixel is the periodic region.