An outdoor unit, connected with indoor units by pipes to constitute a refrigerant circuit, includes a compressor configured to compress and discharge refrigerant, a plurality of parallel heat exchangers configured to allow heat exchange between air and the refrigerant, a first defrosting pipe serving as a flow path for branching a part of the refrigerant discharged by the compressor and allowing the refrigerant to flow into the parallel heat exchanger to be defrosted for defrosting, a first expansion device configured to decompress the refrigerant passing through the first defrosting pipe, a second expansion device configured to adjust the pressure of the refrigerant that passed through the parallel heat exchanger to be defrosted, and a controller configured to control the second expansion device such that the pressure of the refrigerant that passed through the parallel heat exchanger to be defrosted falls within a predetermined range.