An inverter unit includes a DC power source, an inverter circuit having two or more pairs of switching elements which are connected in parallel to the DC power source, so that a DC voltage of the DC power source is converted into a pulse train-like, pseudo-AC voltage output from the inverter circuit, and a PWM generator connected to the inverter circuit for adjusting the pseudo-AC voltage by pulse width modulation. Further, the inverter unit includes a voltmeter for detecting an actual, output voltage which is output from the inverter circuit, and a duty cycle controller for controlling an output duty cycle, so that the detected, actual, output voltage becomes a target output voltage. In this inverter unit, a desirable, output voltage may be obtained stably and accurately even if a voltage of a power source fluctuates.