When a first temperature difference is the difference between a saturated gas temperature of a first refrigerant at an inlet side and a saturated liquid temperature of the first refrigerant at an outlet side in a heat exchanger for heating, and when a second temperature difference is the difference between a saturated gas temperature of a second refrigerant at an outlet side and a temperature of the second refrigerant at an inlet side in the heat exchanger for heating, the difference between the first temperature difference and the second temperature difference is held in a predetermined value or less by charging the second refrigerant to the second refrigeration cycle so that a plurality of single refrigerants forming the second refrigerant have a predetermined mixing ratio.