An air conditioner includes a refrigerant circuit that includes a heat source heat exchanger configured such that refrigerant flows in from below and flows out from above when the heat source heat exchanger functions as an evaporator of the refrigerant and a plurality of utilization heat exchangers. When the heat source heat exchanger is caused to function as an evaporator, the refrigerant discharged from a compression mechanism is bypassed to an intake side of the compression mechanism via a first bypass circuit, the heat source heat exchanger is caused to function as a condenser, and an expansion valve is closed, whereby refrigerating machine oil accumulating inside the heat source heat exchanger is returned to the intake side of the compression mechanism from a lower portion of the heat source heat exchanger via an oil returning circuit.