PURPOSE: To prevent separation of rust preventive paint by expanding the axial width size of a runner vane in both directions to the width of a guide vane passage at the side of a runner inlet.

CONSTITUTION: Flowing water is led into a runner 1 from the upstream side through a guide vane 3, thereby rotating this runner 1. Axial with Br of a runner vane 6 is constituted so as to become larger to passage width Bg of the guide vane 3. Rust preventive paint applied to a root part of the runner vane 6 will not be separated because the flowing water coming into the runner 1 will not directly collide with the root part of the runner vane 6 in keeping it in high energy intact.