Coded, or compressed data of moving pictures is received through a transmission path. The picture type of the compressed data is detected from the received compressed data of moving pictures. If the picture type of the received compressed data of moving pictures is found to be intra picture, predetermined image data is supplied to a monitor so that it can be displayed on the monitor, and also to a memory so that it can be stored in the memory. If the picture type of the detected compressed data is found to be inter picture, the image data resulting from decoding the received compressed data and the image data stored in the memory are added together, and the data resulting from the addition is supplied to the monitor so that it can be displayed on the monitor and also to the memory so that it can be stored in the memory. Therefore, the image to be monitored and to be cautious about can be displayed on the monitor.