Abstract: Anode voltages A′ and B′ corresponding to video signals A and B are switched by a first switch and supplied to an anode. Cut-off voltages A and B corresponding to the video signals A and B are switched by a second switch and added to a video signal by an adder. A resultant signal is supplied to a cathode. In a CRT, the luminance rises in association with the step-down of the cut-off voltage and the step-up of the anode voltage and the resolution rises in association with the step-up of the cut-off voltage and the step-up of the anode voltage. The first and second switches are switched in accordance with the format of the input video signal respectively, thereby properly selecting the anode voltage which is applied to the CRT and the cut-off voltage. The video image can be displayed by the CRT at the luminance and resolution according to the video signal without changing a driving voltage.