Power transmission member such as gears with high breaking strength of the edge portion (A) of the root and high spalling resistance of the tooth side (B) is obtained. The work such as gears, etc. is cooled after carburization by plasma carburizing, etc. and the work surface is high-frequency hardened, and for heating at the time of high-frequency hardening, the heating conditions are set in such a manner that the heating temperature at the root becomes higher than that at the tooth side and time for holding to high temperature becomes long. This promotes solid solution of carbonate at the root and increases the remaining austenite volume after hardening (25-35% for a good-rule-of-thumb) as well as improves toughness at the edge. On the other hand, on the tooth side, the remaining austenite volume decreases (5-15% for a good-rule-of-thumb) and spalling resistance improves.