Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method

A method of inductively heat treating a treatment object, comprising:

• arranging a second heating conductor portion of a second heating coil at a second distance from a rotational axis to face a convex treatment region of the treatment object, the convex treatment region having an outermost surface with a second radius relative to the rotational axis, the second distance being greater than the second radius;
• arranging a first heating conductor portion of a first heating coil at a first distance from the rotational axis that is smaller than the second radius, to face a concave treatment region of the treatment object having a different position along the rotational axis than the convex treatment region and having an outermost surface with a first radius that is smaller than the second radius;
• and
• moving the treatment object relative to the first and second heating conductor portions along a circumferential direction of the treatment object while inductively heating the convex treatment region using the second heating conductor portion and inductively heating the concave treatment region using the first heating conductor portion, such that the convex treatment region and the concave treatment region form one continuous heating treatment region.