AXIAL FLOW WATERWHEEL POWER GENERATION DEVICE

PROBLEM TO BE SOLVED: To provide an axial flow waterwheel power generation device capable of increasing a velocity of flowing water flowing into a runner, and improving self-startability.SOLUTION: An axial flow waterwheel power generation device 10 in an embodiment is immersed with flowing water and generates power by the flowing water. The axial flow waterwheel power generation device 10 comprises: an outer cylindrical body 11 extending in a main flow direction P of the flowing water and gradually enlarged in the main flow direction P; and an inner cylindrical body 13 at least one part of which is provided inside the outer cylindrical body 11. A runner 14 is arranged inside the outer cylindrical body 11. The runner 14 is rotatably provided on the inner cylindrical body 13, and is rotated by the flowing water with a rotation axial line X extending in the main flow direction P as a center. A power generator 15 for generating power by rotation of the runner 14 is built in the inner cylindrical body 11. An extension piece 20 extending outward in a radial direction from a downstream end 11d is provided at the downstream end 11d of the outer cylindrical body 11.