A frequency-variable filter has a GmC filter having a plurality of OTAs and a capacitor; and a pseudo-random value generator outputting pseudo-random value of which average value in a predetermined time corresponds to an input setting value. And at least an OTA for determining a cut-off frequency, out of the plurality of OTAs, is controlled so that transconductance thereof is variably-controlled according to the pseudo-random values, and the cut-off frequency is variably-controlled based on the input setting value.