A heat-insulating mechanism in a compressor which introduces refrigerant gas from a suction pressure region to a compression chamber and discharges the refrigerant gas from the compression chamber to a discharge pressure region has a circular passage, a communication passage, a cylindrical member and a passage heat-insulating member. The circular passage, which is a portion of the suction pressure region, has a circular cross-section, and is in communication with an external refrigerant circuit. The communication passage, which is a portion of the suction pressure region, intersects the circular passage for connection therewith, and is communicable with the compression chamber. The cylindrical member is fitted into the circular passage. The passage heat-insulating member made of an insulating material covers at least a portion of a passage wall surface which forms the communication passage. Rotation of the cylindrical member is prevented by engaging the passage heat-insulating member with the cylindrical member.