PURPOSE: To prevent the burning of a substrate due to a high voltage arc discharge.

CONSTITUTION: A detection negative pattern 28 is provided at the surrounding of a deflection current circuit 14, one edge side is connected through a terminal 19 with a power supply voltage E1, and the other edge side is connected with a discharge detecting circuit 35. When the disconnection of a negative pattern 20 is detected by the Zener breakdown of a Zener diode ZD 11, or the disconnection of the negative pattern 20 and the detection negative pattern 28 is detected as a state change from the turning-off to the turning-on of a transistor Q3, a disconnection detection signal is supplied from the discharge detecting circuit 35 to a deflection processor 37, and a horizontal oscillation operation is stopped. Then, horizontal deflection currents are prevented from flowing, and the arc discharge can be stopped.