A fiber-optic interferometric temperature sensor is fabricated using a hollow optical fiber with 8 um air hole. This interferometric sensor for measuring temperature consists of 13 mm long hollow optical fiber whose one end is attached to the single mode fiber and the other end is cleaved. After the sensor is put in a furnace, the phase change of the sensor output signal is measured as the temperature of the furnace increases from $28^{circ}C$ to $100^{circ}C$. The phase change of the fiber sensor is proportional to the change of temperature and the relationship between the change of phase and temperature is approximately linear. The sensitivity of this sensor is $2.7{;}radians/^{circ}C$.