To transmit R, G, B image data through an identical transmission path by receiving serial image data, separating the data into R, G, B image data, storing the data to a frame memory for each color, reading the stored data at a prescribed speed, and output the R, G, B data.

R image data are written and stored in a 1st frame memory 4r via a write changeover section 3r at an input image data transfer speed for one vertical period. Furthermore, a read changeover section 6r outputs R image data stored in a 2nd frame memory 5r to a multiplexer 7. A control section 8 is used to allow a multiplexer 7 controlled 9, in linking with the operation of the 1st and 2nd frame memories 4r, 5r and the read changeover section 6r to select the R, G, B image data, and the serial image data are sent to a transmission section 9 at a seed in compliance with a transmission line transmission speed. An infrared-ray signal from the transmission section 9 is converted into an electric signal by a light-receiving element of a reception section 19, and a demultiplexer 17 controlled by a memory control section 18 demultiplexes the received signal into R, G, B image data.