A plasma-generation power-supply device includes a transformer connected to an alternating-current power-supply, a rectifier connected to the transformer, an inverter connected to the rectifier, a reactor inserted in series in a power line of an ozonizer that is supplied with power from the inverter, and a controller that controls the inverter. The controller detects the current flowing to the ozonizer with a current detector and provides a control that keeps power applied to the ozonizer constant.