PURPOSE: To improve picture quality by omitting useless processing such as motion detection or motion compensation and improving the encoding data rate of a dynamic image when a still picture is contained in an image source to be inputted.

CONSTITUTION: A motion detection circuit 4 detects motion vector data from the image data of preceding and following frames inputted to a frame memory 3, a motion compensation circuit 5 calculates motion predictive data based on the motion vector data, and an encoder circuit 6 generates and transmits encoded data based on image data from the encoder circuit 6 and the motion predictive data. An added area designation circuit 8 designates a still picture area in the frame memory 3 and applies those area designation data to the motion detection circuit 4 and the motion compensation circuit 5. The motion detection circuit 4 and the motion compensation circuit 5 omit the processing of motion detection and motion compensation concerning the still picture area.