PURPOSE: To improve the SNR of a multiple signal by raising a multiple level higher than that of other area, in an area which is called an overscan part and does not appear on a display screen, and lowering the multiple level in other part, and executing the transmission.

CONSTITUTION: As for an input signal, a rearrangement of the signal. is executed, and it is assumed that a multiple signal is superposed to the upper and the lower bar parts. In this case, on a transmitting side, by a line counter circuit 2 for inputting a synchronizing signal, a line counter value is outputted, and based on the counter value, a coefficient for controlling a multiple level is generated by a coefficient generator 5. By multiplying this coefficient by an input signal by a multiplier 1, a desired signal is obtained. On the other hand, on a receiving side, as well, a line counter value is outputted by a line counter circuit 5, and based on the counter value, a coefficient for controlling a level expansion is generated by a coefficient generator 6. By multiplying this coefficient by an input signal by a multiplier 4, a desired signal is obtained.