PURPOSE: To facilitate installation and obtain power stably by a method wherein a proper number of floats are connected in parallel by connecting pieces with constant intervals and a proper number of water turbines are provided between the floats.

CONSTITUTION: The hollow water-tight floats 21 of synthetic resin, which are moored in a river by wires, are arranged in parallel with constant intervals and each of them are connected by the connecting pieces 22. Bearings 23 are secured to the floats 21 by using attaching screws and a generator is rotated through chains or the like. The whole of the water turbines are floated at a given height on a water surface by the buoyancies of the floats and the blades of the water turbines may be rotated at proper positions.