A screw compressor (100, 101, 102) comprising: a casing forming an outer shell; a screw shaft disposed in the casing and configured to be driven to rotate; a screw rotor, fixed to the screw shaft, that has a spiral tooth groove in an outer circumferential surface thereof; a gate rotor having a plurality of gate rotor tooth portions configured to fit into the tooth groove of the screw rotor and forming, together with the casing and the screw rotor, a compression chamber in which to compress refrigerant; a slide valve configured to slide in a direction parallel to an axis of rotation of the screw rotor; a bearing housing having a bearing inside and having an outer peripheral surface, the bearing being configured to support one end of the screw shaft so that the screw shaft is able to rotate; and an oil separator configured to separate oil mixed into refrigerant compressed in the compression chamber; characterized in that: the slide valve is provided in a slide groove formed in an inner cylindrical surface of the casing, the slide valve slides on the outer peripheral surface of the bearing housing, and the screw compressor (100, 101, 102) further comprises a heating mechanism connected to the oil separator and configured to, by utilizing oil separated by the oil separator, thermally expand the bearing housing in a radial direction during operation, wherein the heating mechanism includes an oil passage formed in a wall of the casing facing the bearing housing and connected to the oil separator, and a groove portion formed in the bearing housing and configured to communicate with the oil passage, and the heating mechanism is configured to circulate oil separated by the oil separator to the groove portion through the oil passage to thermally expand the bearing housing in a radial direction during operation. a casing forming an outer shell; a screw shaft disposed in the casing and configured to be driven to rotate; a screw rotor, fixed to the screw shaft, that has a spiral tooth groove in an outer circumferential surface thereof; a gate rotor having a plurality of gate rotor tooth portions configured to fit into the tooth groove of the screw rotor and forming, together with the casing and the screw rotor, a compression chamber in which to compress refrigerant; a slide valve configured to slide in a direction parallel to an axis of rotation of the screw rotor; a bearing housing having a bearing inside and having an outer peripheral surface, the bearing being configured to support one end of the screw shaft so that the screw shaft is able to rotate; and an oil separator configured to separate oil mixed into refrigerant compressed in the compression chamber; characterized in that: the slide valve is provided in a slide groove formed in an inner cylindrical surface of the casing, the slide valve slides on the outer peripheral surface of the bearing housing, and the screw compressor (100, 101, 102) further comprises a heating mechanism connected to the oil separator and configured to, by utilizing oil separated by the oil separator, thermally expand the bearing housing in a radial direction during operation, wherein the heating mechanism includes an oil passage formed in a wall of the casing facing the bearing housing and connected to the oil separator, and a groove portion formed in the bearing housing and configured to communicate with the oil passage, and the heating mechanism is configured to circulate oil separated by the oil separator to the groove portion through the oil passage to thermally expand the bearing housing in a radial direction during operation. the slide valve is provided in a slide groove formed in an inner cylindrical surface of the casing, the slide valve slides on the outer peripheral surface of the bearing housing, and the screw compressor (100, 101, 102) further comprises a heating mechanism connected to the oil separator and configured to, by utilizing oil separated by the oil separator, thermally expand the bearing housing in a radial direction during operation, wherein the heating mechanism includes an oil passage formed in a wall of the casing facing the bearing housing and connected to the oil separator, and a groove portion formed in the bearing housing and configured to communicate with the oil passage, and an oil passage formed in a wall of the casing facing the bearing housing and connected to the oil separator, and a groove portion formed in the bearing housing and configured to communicate with the oil passage, and the heating mechanism is configured to circulate oil separated by the oil separator to the groove portion through the oil passage to thermally expand the bearing housing in a radial direction during operation.