The heat treatment method of the present invention includes: a first step of mist cooling a treatment object retained at a prescribed temperature by supplying mist-like coolant, to a target temperature near to and higher than a first transformation point at which a structure of the treatment object begins to be transformed into a prescribed structure; a second step, following the first step, of retaining the treatment object for a prescribed time in a state where supply of mist-like coolant is stopped; and a third step, following the second step, of cooling the treatment object to a temperature lower than or equal to the first transformation point. According to the present invention, it is possible to provide a heat treatment method capable of suppressing irregularity and deformation in the structure of the treatment object.