PURPOSE: To prevent doming or white level distortion without decreasing the contrast of the entire screen with respect to a primary color signal from a teletext decoder or a CAPTAIN broadcast decoder.

CONSTITUTION: A discrimination means 3 discriminates whether or not an output primary color signal relates to a white color according to the entire brightness mode and when it is discriminated that the output primary color signal relates to a white color according to the entire brightness mode, a brightness level generating circuit 2 controls the primary color signal level to the white color use entire brightness level lower than that of the other entire brightness mode. As a result, the brightness level of the output primary color signal relating to a white color according to the entire brightness mode is decreased thereby preventing doming or white level distortion. Thus, since the brightness level of the primary color signal with respect to the other color in the entire brightness mode is left large, the entire contrast of the picture is not reduced.