PURPOSE: To compensate variation in the brightness of a screen with CRT temperature even after heater temperature becomes stable by detecting the temperature of a CRT and controlling at least either of the beam quantity or acceleration quantity of the screen after the heater temperature becomes stable.

CONSTITUTION: The temperature of a heater 3 rises after the power source is turned on, and a cathode 4 is warmed. When a temperature detection signal is inputted, a temperature characteristic adding circuit 8 applies a cathode control circuit 9 with a voltage corresponding to the reverse characteristic of brightness variation corresponding to the temperature. Then the circuit 9 controls the DC voltage of a video modulation signal applied to the cathode 4 to increase or decrease the generation amount of an electron beam. Consequently, the brightness can be stabilized even after the heater temperature is stabilized. The same effect is obtained by controlling the beam acceleration quantity or acceleration quantity and beam quantity.