In an image processing apparatus, degradation of edges of stationary subjects can be suppressed in a moving image obtained by converting moving image data having F frames per unit time into moving image data having 2F sub frames per the unit time. For this purpose, pixel data is inputted in order of raster scanning into an input terminal. Then three contiguous pixel data X1 to X3 are obtained by the input terminal and two delay circuits. A differentiator calculates a difference d1 (=X1−X2) between the pixel data of interest X2 and the neighbor pixel data X1 and a difference d2 (=X3−X2) between the pixel data of interest X2 and the neighbor pixel data X3. A multiplier coefficient for low-pass filter calculation is determined based on the differences d1 and d2, and pixel data X2′ is calculated as pixel data after filter-processing of the pixel data of interest X2.