To provide a motion detection circuit capable of raising encoding efficiency, without causing deterioration of the image quality.

A comparator 9 compares a differential absolute value sum input from an image calculator 11 having a threshold, and based on the comparison results, an internal motion vector threshold or a motion vector to be input from the image calculator 11 is output to a motion detection part 3 as a motion vector. The motion detection part 3 generates an address shifted, corresponding to the motion vector to be input from the comparator 9 to output to a memory 2; calculates as absolute value, the difference between a reference signal shifted, corresponding to the motion vector from a normal search start coordinate and a source signal to be input from a filter circuit 1; searches for the motion vector, in which the value of the differential absolute value sum is minimized; outputs a minimal differential absolute value sum; and outputs the motion vector of that time.