The present invention is a thermal processing unit including: a heating-furnace body whose upper end has an opening; a reaction tube consisting of a single tube contained in the heating-furnace body; a gas-discharging-unit connecting portion formed at an upper portion of the reaction tube, the gas-discharging-unit connecting portion having a narrow diameter; a substrate-to-be-processed supporting member for supporting a substrate to be processed, contained in the heating-furnace body; and a heating unit for heating the substrate to be processed supported by the substrate-to-be-processed supporting member. The heating unit has: a first heating portion arranged around the reaction tube, a second heating portion arranged around the gas-discharging-unit connecting portion, a third heating portion arranged around an upper portion of the reaction tube, a fourth heating portion arranged around a lower portion of the reaction tube, and a fifth heating portion arranged under the substrate-to-be-processed supporting member.