Reduced is occurrence of hunting in which a power factor corrector continuously turns on and off alternately for a short period of time. A power factor correction controller turns on a power factor corrector if a parameter value for an input current into the power factor corrector is greater than or equal to a first threshold, and turns off the power factor corrector if the parameter value is smaller than or equal to a second threshold below the first threshold. Through a predetermined time period from a moment when the power factor corrector is switched either from on to off or from off to on, the power factor correction controller maintains a state of the switched power factor corrector, regardless of the parameter value.