To shorten the time required for induction-hardening of one piece of crankshaft.

An induction-hardening apparatus is constituted of a first hardening station 100 induction-hardening of a first pin group G1 composed of three pins P1, P2, P4 of a first, a second and a fourth pins, a second hardening station 200 for induction-hardening of a second pin group G2 composed of three pins P3, P5, P6 of a third, a fifth and a sixth pins, and a third hardening station 300 for induction-hardening of all of a first to a fourth journal parts J1-J4 in the crankshaft having six cylinder engines. In this induction-hardening apparatus, a handling part for moving the crankshaft W from the first hardening station 100 to the second hardening station 200 and from the second hardening station 200 to the third hardening station 300, and one set of generator for simultaneously supplying high frequency electric power into three current transformers 110A-110C in the first hardening station and three current transformers 210A-210C in the second hardening station 200, are provided.

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