A testing device of an inverter device includes a power supply device including an AC-DC conversion circuit for converting AC power received from an AC power supply into DC power and a control part for controlling the AC-DC conversion circuit and a filter circuit interposed between a tested inverter device to be tested and the power supply device, having a reactor and a capacitor, and delivering the DC power output from the power supply device to the tested inverter device. The control part is configured to execute output adjustment of the AC-DC conversion circuit when a test start signal is generated to start an instantaneous voltage abnormality test which is a test changing magnitude of power supply voltage of the AC power supply in a predetermined direction being either one of increase or decrease during operation of the tested inverter device and the power supply device.