A signal separation unit (101) separates an input picture made up of component pictures of RGB, each of which has an equal number of pixels as the input picture, into three component pictures, and outputs the three component pictures. Each of coding units (102 to 104) codes one of the component pictures into an intra-picture prediction coded picture or an inter-picture prediction coded picture, and outputs a bit stream corresponding to the component picture. A bit stream multiplexing unit (105) multiplexes three bit streams outputted from the three coding units into one bit stream, and outputs the bit stream. Each of the coding units (102), (103) and (104) determines a prediction method for the component picture at the time of coding.