Provided is a power generation device which, by causing a rotating member to rotate using the flow of a plurality of fluids, is able to stabilize the rotation of the rotating member and perform stable power generation.　The power generation device is equipped with a floating base 10 that is provided with a flow passage 11 through which a fluid flows, a rotating member 20 that is rotatably supported by a support part 1 provided upon the floating base 10 and rotates about an axis by means of the flow of the fluid through the flow passage 11, and a rotation transmitting mechanism 60 that transmits the rotation of the rotating member 20 to a power generation part 50 installed upon the floating base 10. On the inlet opening 11a side of the flow passage 11 in the floating base 10, a fluid introduction part 30 is formed that takes in wind and water as fluids from an intake opening 31 formed to have a larger opening area than the inlet opening 11a and causes the fluids to flow into the inlet opening 11a.