To provide a catamaran-type water turbine propeller generator that stably generates electricity regardless of a vertical fluctuation in water level of a river, when river current energy is converted to the electricity.

A catamaran is configurated by arranging two reinforced plastic boats in parallel, providing connection materials E in forefront and rearmost parts, respectively, and providing a device installation base F in the center. In a catamaran-type water turbine propeller generator, a generator B is provided in the central part of the device installation base F; a water turbine propeller A is provided ahead of the generator on the base; and a water turbine propeller A is provided in the rear of the generator.