A loading unit avoiding the need to enhance the performance of a lifting elevator mechanism, thus preventing an increase in the cost of the lifting elevator mechanism. The loading unit is configured to vertically move a substrate holder, holding a plurality of substrates, into and out of a cylindrical processing container upon heat treatment of the substrates. The loading unit includes: a lifting elevator mechanism for holding and vertically moving the substrate holder and a cap; and a pressing mechanism, having a piezoelectric actuator, for upwardly pressing against the cap lying at a bottom opening of the processing container.