For the purpose of coding or decoding motion information in a picture with a small overhead, a coding method of performing compression coding of a moving picture by motion compensated prediction is configured to have a motion compensated prediction step (processing by motion detector 2, motion compensator 5, spatial predictor 9, etc.) of performing the motion compensated prediction while assigning one or more motion vectors (e.g., up to two motion vectors) in units of sub-blocks obtained by sub-dividing each of macroblocks resulting from division of each frame of the moving picture; and an assignment information coding step (processing by variable length encoder 23 and others) of outputting information about an assignment situation of the one or more motion vectors to the sub-blocks in a multiplexed form on a bitstream.