A heat treatment apparatus includes a furnace body in which a material is transferred and heat treated, a sagger disposed inside the furnace body and configured to receive and transport the material, a roller configured to transport the sagger, and a heater disposed at a position apart from the sagger. The sagger seated on the roller includes a plurality of saggers. The heater includes an upper heater disposed above the sagger and a lower heater disposed under the sagger, based on a third direction which is a height direction of the furnace body, and the lower heater is disposed closer to the roller than to a bottom surface of the furnace body.