A single-screw compressor includes a screw rotor, a cylinder wall in which the screw rotor is rotatably accommodated, a driving mechanism which variably drives the screw rotor according to a load, and a slide valve which is provided in a slide groove formed in the cylinder wall. The slide valve faces an outer circumferential surface of the screw rotor to be movable in an axial direction, and to adjust a discharge start position by being moved in the axial direction according to the operating capacity. A discharge side end surface of the slide valve extends in a direction corresponding to a screw land of the screw rotor to which the discharge side end surface faces when the slide valve is moved to a position corresponding to a part load operation state.