Heat treatment apparatus

A heat treatment apparatus, comprising:

• a processing container having a roof in a cylindrical shape and a lower end opening, and in which a first space is formed;
• a lid configured to close the lower end opening;
• a support provided to pass through the lid and including a shaft portion and a placement portion located above the shaft portion;
• a boat installed on the placement portion and configured to hold a plurality of substrates arranged in multiple stages in a vertical direction;
• a partitioning member provided around the shaft portion with a gap left from a lower surface of the placement portion and configured to form a second space partitioned from the first space;
• and
• a heat insulating material provided in the second space,
• wherein an exhaust port is provided in a portion of a sidewall of the processing container,
• in a circumferential direction of the processing container, the gap includes a first gap having at least an angular position where the exhaust port is provided, and a second gap provided at an angular position excluding the first gap, and
• the first gap is wider than the second gap.