PURPOSE: To secure a long service life of the blade by irradiating the laser beam in the vicinity of the connected part of a diamond chip of a blade part of a road cutting rotary blade to a base steel plate through the optical system, and achieving the laser beam welding and the laser beam quenching.

CONSTITUTION: The laser beam is radiated through the optical system of the boundary part 3 between a diamond chip 1 of a blade part of a road cutting rotary blade and a base steel plate 2, and the laser beam welding is achieved in this irradiated part. Then, the quenching to the depth of approximately 0.2mm is achieved by irradiating the laser beam on the surface. These treatments allow not only the cutting capacity to be improved, but also the hardness of the connected part to be increased, and abnormal abrasion of the blade part may be suppressed in cutting the road containing stones, and a road cutting blade of longer life is obtained.