PURPOSE: To evaluate the frequency characteristic of a switched capacitor filter (SCF) circuit part and to reduce product cost, by inputting a square wave of a determined cycle to the SCF circuit part and discriminating the change of output voltage.

CONSTITUTION: Switches 51, 52 are connected so as to test an analogue circuit part 3 and switches 61, 62 are connected so that an SCF circuit part 4 is connected to a digital tester 5 in a continuity state. Then, a square wave is inputted to the input terminal 41 of the circuit part 4 from the tester 5 through the switches 51, 61. When the internal circuit of the circuit part 4 is normal and the frequency of the square wave is present in the pass-band of the circuit part 4, a sine wave having frequency corresponding to the output waveform thereof is outputted. Said sine wave is sampled at a definite time interval by the tester 5 and high level reference voltage or more is judged to be 1 and below low level reference voltage is judged to be 0 and a range from below high level reference voltage to low level reference voltage is judged to be indefinite. When frequency is within the cut-off region of the circuit part 4, the width between the bias voltage value of the circuit part 4 and a reference voltage value is preset to 1/21/2 the amplitude of the output voltage value of the pass-band frequency thereof.