To digitally generate a sawtooth wave in order to attain the vertical deflection with high accuracy.

The optional prescribed value A is set by a setting means 1 and supplied to an accumulation circuit 2 which adds (accumulates) the value A for every optional clock that is sent from a terminal 3. When the circuit 2 is reset by a vertical synchronizing signal V sent from a terminal 4, the data on a vertical sawtooth waveform are outputted with high accuracy. Then a generation circuit 6 reads out the data calculated or stored in a memory, etc., for every horizontal synchronizing signal H received from a terminal 7 in order to generate the data on a corrected wave of accuracy (e.g. 18 bits) equivalent to the data on the vertical sawtooth waveform. The data on the corrected waveform are supplied to an addition circuit 5, and the data on upper 14 bits, for example, of the addition data of the circuit 5 are supplied to a vertical deflecting coil 10 via a D/A converter 8 and an output amplifier 9.