PURPOSE: To realize a scanning line interpolation processing where the picture quality is not degraded even in dynamic pictures, by utilizing a frame difference signal between two adjacent fields to extract motion information of an object.

CONSTITUTION: When field memories 21, 23, and 24 and line memories 22 and 25 are cascaded, positional relations of time/space between their input and output signals appear as signals on scanning lines 14∼19. A signal of an interpolating scanning line 20 is calculated in accordance with a formula by adding circuits 26, 28, and 32, coefficient circuits 27 and 29, and multiplying circuits 30 and 31 (0≤k≤1). In this formula, a motion coefficient (k) is approximated to "1" in the part of a still picture and is approximated to "0" in the part of a dynamic picture. A motion detecting circuit consists of subtracting circuits 33, 35, and 37, absolute value circuits 34, 36, and 38, an adding circuit 39, and a coefficient converting circuit 40, and the motion coefficient (k) is obtained as the output of the coefficient converting circuit 40 which sets (k) to "1" if a signal resulting from addition of absolute values of three frame difference signals (14-17), (15-19) and (16-18) is small and approximates (k) to "0" according as this signal is larger.