A decoding execution unit decodes image data encoded with a resolution higher than that of a display device. A display buffer stores image data decoded by the decoding execution unit. A standby buffer stores image data decoded by the decoding execution unit while the image data stored in the display buffer is being displayed. A reduced image buffer stores image data produced by reducing the entirety of the image data. An image display control unit switches from the image data stored in the display buffer to the image data stored in the standby buffer if the decoding of the image data by the decoding execution unit is completed, and enlarges the image in the reduced image buffer and stores the enlarged image in the display buffer if the decoding of the image data by the decoding execution unit is not completed.