A power conditioner includes an inverter unit and a control unit that outputs an error signal indicating a mounting error of a first or second current sensor based on a result of detection by the first current sensor and a result of detection by the second current sensor. When output from the inverter unit is varied by a first threshold value or higher during a first predetermined time period, the control unit outputs the error signal if a detection value of the first current sensor is not varied with the variation in the output from the inverter unit during a second predetermined time period and outputs the error signal if a detection value of the second current sensor is not varied with the variation in the output from the inverter unit during the second predetermined time period.