An inverter power source for a high frequency heating apparatus, said inverter power source being adapted to supply an electric power to the high frequency heating apparatus by rectifying an alternating current output from an alternating current source to a direct current output and inverting the direct current output to a desired alternating current output by applying a drive signal, based on a start signal formed by a PWM control signal, to a switching element, which inverter power source comprises: (a) an electric power source abnormality detecting circuit in a form of an analog circuit including a start signal abnormality detector for detecting an abnormal PWM control signal, a temperature abnormality detector for detecting an abnormal temperature of the switching element made of an IGBT element, a voltage abnormality detector for detecting an abnormal drive signal to be applied to the switching element, and a current abnormality detector for detecting an abnormal input current; (b) an inverter switching drive circuit operable to output an abnormality control signal to the switching element to halt oscillation of the switching element and therewith the inverter power source in response to an abnormality detection signal fed from at least one of those abnormality detectors; characterized by (c) a latch inhibiting circuit provided in at least one of the start signal abnormality detector, the temperature abnormality detector and the voltage abnormality detector for inhibiting latch of the detected abnormal state of the abnormality detecting circuit whereby the current abnormality detector is inhibited from detecting the abnormal input current based on a halt of the oscillation brought about by the detection of at least one of the start signal abnormality, the temperature abnormality and the voltage abnormality. (a) an electric power source abnormality detecting circuit in a form of an analog circuit including a start signal abnormality detector for detecting an abnormal PWM control signal, a temperature abnormality detector for detecting an abnormal temperature of the switching element made of an IGBT element, a voltage abnormality detector for detecting an abnormal drive signal to be applied to the switching element, and a current abnormality detector for detecting an abnormal input current; a start signal abnormality detector for detecting an abnormal PWM control signal, a temperature abnormality detector for detecting an abnormal temperature of the switching element made of an IGBT element, a voltage abnormality detector for detecting an abnormal drive signal to be applied to the switching element, and a current abnormality detector for detecting an abnormal input current; (b) an inverter switching drive circuit operable to output an abnormality control signal to the switching element to halt oscillation of the switching element and therewith the inverter power source in response to an abnormality detection signal fed from at least one of those abnormality detectors; characterized by (c) a latch inhibiting circuit provided in at least one of the start signal abnormality detector, the temperature abnormality detector and the voltage abnormality detector for inhibiting latch of the detected abnormal state of the abnormality detecting circuit whereby the current abnormality detector is inhibited from detecting the abnormal input current based on a halt of the oscillation brought about by the detection of at least one of the start signal abnormality, the temperature abnormality and the voltage abnormality.