Abstract: A vertical heat treatment apparatus which has a vertical processing vessel with heat source, and a loading mechanism for holding an object to be treated and for loading and unloading the object into and out of the processing vessel through its bottom. The loading mechanism includes an outer cylindrical shaft which is moved up and down by a lift drive unit, a liner plate disposed on the upper end of the outer rotary shaft, and a rotary holder which is disposed in the liner plate and is moved up and down independently of the liner plate. As a result, a large object to be treated, such as a large-diameter semiconductor wafer, LCD substrate, etc., can be rapidly heated up to a required treatment temperature while uniform temperature distributions are attained. Thus, heat-treatments of high precision can be efficiently conducted.