A heat treatment apparatus performs a heat treatment on a plurality of target objects held by a holding unit while allowing an inert gas to flow upwardly in a vertical processing container with at least one heating unit provided in the vicinity of the processing container. The heat treatment apparatus includes: a main temperature control unit configured to control the heating unit; an inert gas passage through which the inert gas flows into the processing container; an inert gas heating unit installed in the inert gas passage and configured to heat the inert gas; a first temperature measuring unit installed in the inert gas heating unit; and a temperature controller configured to control the inert gas heating unit based on temperatures measured by the first temperature measuring unit.