Abstract: A road-ice detecting sensor includes: a temperature sensing member of T shape made of a highly heat conductive metal, having a temperature sensor to be grounded onto a road and a fin part erected from this temperature sensor; an optical fiber having an FBG bonded onto the fin part of the temperature sensing member; and a case having a heat insulating member surrounding the fin part of the temperature sensing member and the optical fiber. A plurality of number of the read-ice detecting sensors are installed on a road, connected to one another via an optical cable. Pulsed light is launched into one of the ends of the optical cable, and beams of reflected light from the respective road-ice detecting sensors are received to measure the road temperature.