To provide a fan controller capable of utilizing natural winds more efficiently than before.

The fan controller includes: an AC motor 8M for driving a fan; a power source part 2 for rotating the AC motor 8M by supplying power to the AC motor 8M; and a control part 9 for controlling power supply by the power source part 2. When a set determination interval elapses after making the power source part 2 start or restart the power supply, the control part 9 makes the power source part 2 tentatively stop the power supply. Then, during the tentative stop of the power supply by the power source part 2, the control part 9 receives sensing signals Vus and Vvs that change corresponding to the strength of the natural wind, and determines whether or not to make the power source part 2 restart the power supply on the basis of the sensing signals Vus and Vvs.