A heat treatment apparatus includes: a treatment chamber unit that is, inside a furnace shell, detachably fixed to the furnace shell; and a power supply portion, in which the treatment chamber unit includes: a treatment container in which a heat treatment is performed on a workpiece; a heat insulating material provided inside the treatment container; a heater that has a heating element located inside the treatment container and has a terminal located outside the treatment container; and a busbar that is provided on the outside of the treatment container and is electrically connected to the terminal of the heater, the power supply portion is provided outside the treatment container, and the busbar and the power supply portion are detachably connected to each other.