An area detecting unit detects a first matching area in a first reference block in the first reference frame, a second matching area in a second reference block in the second reference frame. A settling unit settles a secondary motion vector to be assigned to a mismatching area in the each interpolation block, based on surrounding interpolation blocks around the mismatching area. A motion compensating unit assigns an image to the interpolation frame based on the primary motion vector and the secondary motion vector.