A high-frequency heating device comprising: an inverter for rectifying an AC power and converting the AC power to a high-frequency power; a boosting transformer for boosting a high-frequency power outputted from said inverter; a high-voltage circuit for converting the output of said boosting transformer to a high DC voltage; a magnetron for receiving said high DC voltage and irradiating a microwave; a first current sensing resistor provided on a first path where the anode current of said magnetron flows, said first current sensing resistor detecting the anode current and being connected to the earth of a first circuit board on which at least said high-voltage circuit is arranged; and a controller for controlling the oscillation of said magnetron by controlling said inverter; characterized by a second current sensing resistor separated from said first current sensing resistor, said second current sensing resistor provided on a second path connected to said first path while branching therefrom and connected to the earth of a second circuit board as a substrate for a control panel the user touches for operation; wherein the controller applies a predetermined voltage to said first current sensing resistor and said second current sensing resistor while said inverter is not operating to determine the earth states for said first circuit board and said second circuit board, and makes control to inhibit start of operation of said inverter assuming an abnormality when determining that at least one of the earths is imperfect and to permit start of operation of said inverter when detecting that neither the earth state for said first circuit board nor the earth state for said second circuit board is imperfect. an inverter for rectifying an AC power and converting the AC power to a high-frequency power; a boosting transformer for boosting a high-frequency power outputted from said inverter; a high-voltage circuit for converting the output of said boosting transformer to a high DC voltage; a magnetron for receiving said high DC voltage and irradiating a microwave; a first current sensing resistor provided on a first path where the anode current of said magnetron flows, said first current sensing resistor detecting the anode current and being connected to the earth of a first circuit board on which at least said high-voltage circuit is arranged; and a controller for controlling the oscillation of said magnetron by controlling said inverter; characterized by a second current sensing resistor separated from said first current sensing resistor, said second current sensing resistor provided on a second path connected to said first path while branching therefrom and connected to the earth of a second circuit board as a substrate for a control panel the user touches for operation; wherein the controller applies a predetermined voltage to said first current sensing resistor and said second current sensing resistor while said inverter is not operating to determine the earth states for said first circuit board and said second circuit board, and makes control to inhibit start of operation of said inverter assuming an abnormality when determining that at least one of the earths is imperfect and to permit start of operation of said inverter when detecting that neither the earth state for said first circuit board nor the earth state for said second circuit board is imperfect.