A power generator according to an embodiment includes a rotor shaft, a slip ring, a detecting shaft, and a position sensor. The rotor shaft through which wires from a propeller are inserted rotates with the propeller. The slip ring is coupled to the rotor shaft at one end. The detecting shaft is provided at the other end of the slip ring and rotates along with the rotor shaft. The position sensor detects the rotational position of the detecting shaft, thereby detecting the rotational position of the propeller.