An apparatus for heat treatment of a heat shrinkable film includes a steam generation apparatus that generates steam, a heated air generation apparatus that generates heated air not lower in temperature than steam generated in the steam generation apparatus, a mixed gas generator that generates mixed gas not lower in temperature than steam generated in the steam generation apparatus by mixing steam generated in the steam generation apparatus and heated air generated in the heated air generation apparatus, a reheating apparatus that generates superheated steam by reheating mixed gas generated in the mixed gas generator, and a supply portion that supplies superheated steam generated in the reheating apparatus to a heat treatment chamber.