PURPOSE: To provide a round chip saw base excellent in quality and useful for cutting grasses, etc., at a low hardening cost without using a heating coil, etc., by rotating roller electrodes to rotate the base and simultaneously harden the prescribed circular part of the base.

CONSTITUTION: A method for hardening a round chip saw comprises rotatably setting a base 2 having chip-attaching parts in the outer periphery to a base table 3, bringing roller electrodes 4, 5 into contact with the front and back surfaces of the base 2, applying a high frequency electric current to the roller electrodes 4, 5, and simultaneously rotating the roller electrodes 4, 5 to rotate the base 2 and simultaneously harden the prescribed circular part of the base 2.