Provided is a heat treatment apparatus which, when simultaneously heating substrates placed on susceptors, is capable of controlling the uniformity of temperature within each substrate. The heat treatment apparatus includes: a reaction tube which performs predetermined treatment to wafers; a plurality of susceptors each of which has a mounting surface for mounting the wafer and is made of a conductive material; a rotatable quartz boat wherein the susceptors spaced apart in a direction perpendicular to the mounting surfaces are arranged and supported in the reaction tube; a magnetic field generating unit which is arranged on a sidewall of the processing chamber and includes a pair of electromagnets which generate an AC magnetic field in a direction parallel to the mounting surfaces of the susceptors and inductively heat the susceptors; and a control unit which controls the AC magnetic field generated by the magnetic field generating unit.