An optical fiber is provided with a first measurement portion and a second measurement portion provided with covering layers different at least in any one of heat capacity and heat conductivity. Then, the first measurement portion and the second measurement portion are located in the same measurement position and light is inputted from a temperature measurement device into the optical fiber. Thereafter, the temperature measurement device receives backscattered light generated inside the optical fiber to measure temperature distribution in a longitudinal direction of the optical fiber. An analyzer analyzes a variation over time of the temperature distribution outputted from the temperature measurement device to calculate a temperature and a wind velocity in a measurement position where the first measurement portion and the second measurement portion are located.