According to this invention, since a region to be decoded in a frame is set in accordance with the playback speed, the load on the decoding process remains unchanged irrespective of the playback speed, and a smooth moving image can be played back within a feasible load range. To this end, when normal playback is designated, a frame data decoding unit is set to decode the entire frame at 30 fps. On the other hand, when double-speed playback is designated by a high-speed playback designation, the frame data decoding unit is set to decode a region substantially corresponding to 1/2 the area of a frame at 60 fps.