A clamping circuit for supplying a clamped color signal to a gamma-correction circuit is provided with a clamping portion connected to a clamping voltage generating circuit. The clamping voltage generating circuit generates a clamping voltage in response to an individual control signal in such a way that the black level of a color signal coincides with the black level in an input/output characteristic of the gamma-correction circuit. The clamping portion adds this clamping voltage to the pedestal level of a color signal at a predetermined timing in response to a control signal, so as to absorb variations in black levels of the clamping levels and later-stage circuits including variation in the later-stage circuits.