One embodiment provides a moving picture decoding device for decoding a compression-coded video stream, including: an inverse-quadrature-transformer/dequantizer configured to perform inverse-quadrature-transformation/dequantization processing on each frame to be decoded; a load detector configured to detect a magnitude of an apparatus processing load including a processing load for decoding; a judging module configured to judge whether the magnitude of the apparatus processing load detected by the load detecting module is small; and a controller configured to control the inverse-quadrature-transformer/dequantizer so as to skip at least part of the inverse-quadrature-transformation/dequantization processing if the judging module judges that the magnitude of the apparatus processing load is not small.