An inverter device applies an excitation current to an excitation winding of a step-up transformer through a switching element, and outputs an output voltage with an alternating-current half-wave waveform from an output winding of the step-up transformer. The inverter device includes: an input-voltage detecting unit that detects a state of the input voltage, as a voltage; a current detecting unit that converts a current flowing through the switching element into a voltage to detects the current; and a comparing unit that compares a detected current value detected by the current detecting unit with a detected input voltage value detected by the input-voltage detecting unit, and detects a high-current period in which the detected current value exceeds the detected input voltage value. Based on information indicating the high-current period detected by the comparing unit, the control circuit adjusts a period in which the switching element is turned on.