Abstract: A supplying power adjusting apparatus has excellent temperature response and excellent stabilities to power supply change and load change. The apparatus is provided with a semiconductor inverter for high-speed switching power control, which converts a direct current rectified by a rectifying circuit (10) into alternating current power in response to a control signal and supplies a heater (7) with the power; a temperature change detecting circuit (24) for detecting the temperature change of the heater (7); a power supply change detecting circuit (22) for detecting the power change of the rectifying circuit (10); a load change detecting circuit (23) for detecting the change of the alternating current power supplied to the heater (7); and a power control signal generating circuit (15) which calculates a power quantity to be supplied to the heater (7) and controls the frequency or duty ratio of a control signal to be added to the power controlling semiconductor inverter in response to the calculated results.