Disclosed is hydroelectric power generating equipment (1) wherein, since the equipment is employed in a mode in which all water turbine vanes (22) are concurrently immersed, the immersed volume of a water turbine (20) as a whole is greatly increased, and a considerable portion of the weight of the actual water turbine (20) and the weight of a generator (40) that is connected to the water turbine (20) can be borne by the total amount of buoyancy acting on the water turbine vanes (22). This makes it possible to reduce the weight of and space taken up by the support structure section of the water turbine (20) and generator (40), thereby making it possible to effectively reduce the space and construction costs involved in installing the hydroelectric power generating equipment (1). In this way, by raising the efficiency of conversion of water flow energy to water turbine rotation energy and more effectively utilising the buoyancy acting on the actual water turbine, it is possible to provide hydroelectric power generating equipment in which the weight of the water turbine and the generator can be efficiently supported by a more compact mechanism.