An air conditioner switches between a normal refrigeration cycle and a defrosting refrigeration cycle, and includes: a refrigerant circuit that connects a first heat exchanger, a second heat exchanger, a radiation panel, and an expansion valve that regulates a flow rate of a refrigerant flowing through the radiation panel; and a controller that causes the air conditioner to switch between the normal refrigeration cycle and the defrosting cycle. During the normal refrigeration cycle, the radiation panel performs cooling or heating. During the defrosting cycle, the first heat exchanger serves as a radiator and the second heat exchanger serves as an evaporator. During the defrosting cycle, the controller causes the expansion valve to be in a fully closed state.