A motion amount at a pixel position to be interpolated of a field of interest is calculated. A difference coefficient between frames is calculated based on video signals of two fields which are adjacent to the field of interest and are separated by one frame. A motion intensity between fields is calculated based on video signals of the field of interest and a field after the field of interest. The motion amount is corrected using a predetermined function. The corrected motion amount is corrected again based on the difference coefficient and motion intensity.