PURPOSE: To obtain a motion detector eliminating that an image is erroneously decides as a dynamic image when the image has fine patterns and is not the dynamic image.

CONSTITUTION: The high frequency components in a vertical direction are detected by a high-pass filter by the D latch 202 and subtraction circuit 203 of picture element data, the absolute value is added to an accumulation circuit composed of an addition circuit 205 and a D latch 207, the sum value is obtained, and it is added to a decision circuit 208. The low frequency components in the vertical direction are detected by a low-pass filter by the D latch 211 and addition circuit 212 of picture element data, the absolute value is added to the accumulation circuit composed of an addition circuit 214 and a D latch 216, the sum value is obtained and it is added to the decision circuit 208. When a motion is decided by comparing the high frequency components with a reference value, a reference value is changed according to the low frequency components.