PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a plate-shaped rotary blade that is disposed on the upper surface of a mowing blade, and cuts grass and vine twined around a rotating part.SOLUTION: Two or more teeth 2 having a radial linear part 3 of a fixed width are formed at the front end in the rotation direction on an outer circumferential edge of a circular blade plate A. A cut 4 is provided from the front end toward the rear at the base part of the radial linear part 3 of the teeth 2, and the front part of the teeth 2 provided with the cut 4 is bent into five plate surface directions of the circular blade plate A. A cutting blade 6 is formed at the front end of the teeth 2 by polishing a bent portion 8 protruding from the plate surface 5 along the plate surface 5 of the circular blade plate A.
