PURPOSE: To correct the ununiformity of a luminance on a display screen when a signal is displayed while its display size in the horizontal direction is magnified toward left/right ends relatively in the middle of the display screen in the horizontal direction.

CONSTITUTION: A parabolic voltage in upward convex outputted from a horizontal deflection circuit 4 is inverted by an inversion circuit 11 and the inverted voltage is inputted in a subtractor 8. The subtractor circuit 8 subtracts a pulse voltage of a horizontal deflection period outputted from a high voltage circuit 7 with a parabolic voltage in downward convex and the result is inputted to a contrast adjustment circuit 1. As a result, the voltage of a luminance signal outputted from the contrast adjustment circuit 1 is higher toward left/right ends of the horizontal deflection period and low in the middle to uniformize the luminance on a display screen.