In a Stirling refrigerator, a displacer has an internal space. An expander body houses the displacer so that the displacer can be reciprocated. A temperature sensor is arranged in the internal space of the displacer. A displacer rod, having an internal space, may connect to the displacer. A wiring may provide an electrical connection to the temperature sensor, the wiring arranged through the internal space of the displacer rod to outside of the expander body.