PURPOSE: To obtain automatically a color demodulation output changing based on a constant reference constantly by extracting separately R-Y and B-Y from a color demodulation output of a back porch part in a horizontal return wire period for including a carrier chrominance signal and controlling a reference frequency in a color demodulation circuit for R-Y and B-Y.

CONSTITUTION: The output signal of a transistor 22 is a color demodulation output R-Y for showing the transparency in a back porch part, is amplified in a transistor 27, suppleid to a varactor diode 17 as a control signal H, and controlled so that the color demodulation output for showing the transparency in the back porch part can be a constant value. In a control circuit 18b, the same procedure is executed; a B-Y chrominance signal outputted from an FM demodulation circuit 12b is outputted as a control signal G after its back porch part in a horizontal return wire period is taken out, and controlled so that a colorless part of the color demodulation signal B-Y can be a constant value.