Abstract: The coding mode determining section, when receiving the information as to occurrence of a scene change from the scene change detector, outputs a piece of mode control information to the coding controller. The coding controller, based on the amount of coding in the coder and the mode control information, controls the quantizer by setting up a quantization stepsize so that the current frame will have the target amount of coding. In this way, the quantization and coding are controlled by three stages, i.e., immediately after a scene change, from the scene change to the stabilization of the amount of coding, and after the stabilization of the amount of coding, to thereby prevent degradation of picture quality.