Abstract: A heat treatment apparatus comprising a holder, a hollow cylindrical cover, a flat plate, and a processing chamber. The holder holds disk-shaped objects, each having an orientation flat portion at circumference. The objects are arranged coaxially and spaced at predetermined intervals, with the orientation flat portions aligned with one another. The cover has gas ports and surrounds the objects held by the holder and is spaced from a circumference of each object by a predetermined distance. The flat plate is mounted on an inner surface of the cover and opposes the orientation flat portions of the objects. In the processing chamber, the objects held by the holder are processed by using a process gas.