To provide a low-cost cemented carbide thin plate tool simply correcting a strain and to provide a straightening method for the cemented carbide.

A laser beam 22 is irradiated on a projection part 14a of the strain due to a warp and the like on the surface of a cemented carbide thin plate 14 of a metal saw 10, or the cemented carbide thin plate tool. The laser beam 22 reforms the cemented carbide surface to correct the strain. The irradiation part 20 reformed by the irradiation of the laser beam 22 is also served as a display part of a mark and a symbol displayed on the cemented carbide thin plate 14.