To reduce the risk of penetration of oil into a float.

An oil separator 11 separates oil in refrigerant discharged from a compressor and returns the oil to the compressor. The oil separator 11 includes: a tank 21 into which the refrigerant discharged from the compressor flows; a float 24 having a hollow interior that is formed by welding a plurality of members and is vertically movable according to a change in an oil level in the tank 21; and a needle valve 29 that returns the oil in the tank 21 to the compressor according to the vertical movement of the float 24. The float 24 is disposed so that an end edge 24E of a weld part is located above the oil level.