To enable an increase in a torque amount applied to a blade with simple and low-cost means in a natural energy type power generator. An output reinforcement device of a power generator according to an embodiment is an output reinforcement device of a power generator including a rotor that includes at least one blade driven by renewable energy and a hub attached with the blade, the output reinforcement device including a casing that has a tubular shape and disposed to surround the hub, the casing having a through-hole through which the blade is inserted and being configured to rotate together with the rotor.