To solve the problem that, in the conventional high frequency power supply, a bias current flows into an AB class push-pull method amplifier constituting an amplifying section, resulting in waste of power supply, irrespective of whether or not the power supply is in a standby-period without generating any high frequency power.

When a control switching signal SW1 displays "saving energy control", a DC power supply control unit 10 uses an output prohibiting signal SW2 input from outside to judge whether or not the power supply is in a stand-by period outputting high frequency power. When judged in the stand-by period, the power supply is controlled so that a DC power supply voltage is not supplied from a DC power supply 3 to the amplifier 2, even if power is supplied from a commercial power source 7 to a DC power supply 3. Thus, no bias current flows to the amplifying device 2 during the stand-by period, resulting in eliminating power consumed in waste to reduce power loss.