An encoding system capable of preventing the overflow of a buffer and performing the encoding of a VOP within a predetermined time period even where the processing time period necessary for encoding each macroblock is not constant. In order to provide the encoding system, the maximum number of bits Tmax is set for each VOP, and the output of encoding unit and the output of fixed code output unit is switched and outputted so that the number of bits Sc of the VOP may not exceed the Tmax.