To provide an anemometer, which does not receive the electric adverse effect of external environment, can perform long-distance transmission, can be readily multiplexed and can perform real-time wind-speed measurement.

When a rotating mechanism 1 is rotated by receiving wind, an electric conversion mechanism 2 is operated, and the rotation is converted into electricity. The electricity is converted into pressure by a pressure conversion mechanism. The pressure change can be sensed by an optical-frequency conversion type optical fiber sensor 4 as the frequency shift of the reflected light. The bending loss of the optical sensor 4 is changed by the pressure. The bending loss is sensed based on the accompanied optical-intensity change, and the wind speed can be sensed. The pressure is made to act on the bending part of the optical fiber sensor 4, and the optical path length of the light propagating in the bending part is changed. The pressure change is sensed from the optical intensity change based on the change of the optical path length, and the wind speed can be sensed.