A gain temperature compensation circuit producing a relatively small loss of power, and enabling modification of a variation width of the attenuation amount in a predetermined temperature range is provided. A gain temperature compensation circuit includes a circulator and a thermistor. The circulator outputs a signal being input to a first port to a second port, and outputs the signal being input to the second port to a third port. The thermistor being connected to the second port reflects the signal being output from the second port by varying the power of the signal according to temperature, so as to input to the second port, in order to adjust the attenuation amount of the signal.