PURPOSE: To reduce the size by fixing plural blades in parallel onto the underface of circular flat buoy then rolling a crank rod journaled in the buoy while provided with a weight at one end through rolling motion of buoy produced through the wave force and producing power.

CONSTITUTION: Plural blades 2 are fixed in parallel onto the underface of circular flat buoy 1 in the perpendicular direction against the advancing direction of wave. A shaft 4 is supported through a longitudinal bearing 3 in the buoy 1 at such position as will be proper center of gravity on the center line X-Y of buoy parallel with the blade 2 and a crank rod 5 fixed with a weight 6 is secured to the tip of said shaft 4. The shaft 4 is rotated through the crank rod 5 by the rolling of buoy 1. The rotation of said shaft 4 is increased through gears 7W12 to drive a generator 13.