A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T 1 ) equal to or higher than a tempering temperature (T 0 ) of the second steel component and higher than a temperature of the first steel component by a temperature difference (ΔT) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.