To obtain a triangle wave signal with excellent linearity in which a rising slope and a falling slope are equal to each other by synthesizing a sawtooth wave signal and an inverted sawtooth wave signal outputted alternately so as to generate the triangle wave signal.

A sawtooth wave signal is given to a noninverting circuit 13a and an inverting circuit 13b and a noninverting sawtooth wave signal (a signal at a point C) and an inverted sawtooth wave signal (a signal at a point D) are extracted from the circuits 13a, 13b respectively. Both the signals are given to a switch changeover circuit 15 to select a switch 14 alternately so that the noninverting sawtooth wave signal is outputted when a square wave signal is at a low level and the inverted sawtooth wave signal is outputted when the square wave signal is at a high level. As a result, a triangle wave signal (output signal) is obtained (a signal at a point E). The rising waveform of the triangle wave signal is obtained in a constant current charging process employing a capacitor and the falling waveform of the triangle wave signal is obtained by inverting the rising waveform of the triangle wave signal obtained in the constant current charging process. Thus, the completely symmetrical triangle wave signal is obtained.