To reduce the capacity of a display memory in an MPEG video decoder by providing an image expansion means decoding image data subjected to frame compression and inter-frame compression image data and a control means that allows the image expansion means to conduct the same operation above in 1st and 2nd fields.

The video decoder 1 is made up of a code interface 2, a memory interface 3, an image expansion section 4, a display interface 5 and a controller 6. Then a code buffer memory 7 and a display memory 8 are connected via the memory interface 3 to the decoder 1, and the display memory 8 reserves areas for one frame for I or P picture, one frame for P picture and 16 lines for B picture, in total about 2.1 frames. That is, the memory capacity for the B picture having been required for a conventional memory capacity of at least 0.5 frame is reduced to 16 lines.