To provide a heat treatment device which can take out a heat-treated object from a treatment container and cool it, and can reduce the influence of heat that a fluid seal of a valve receives from the circulation of the object from the treatment container to a cooling unit.

The heat treatment device 1 is provided with the treatment container 11 having an outlet 27 of the object in one side in a horizontal direction, and includes: a heat treatment unit 2 that heat-treats the object housed in the treatment container 11; the cooling unit 3 that is arranged lower than the outlet 27 of the treatment container 11, and cools the heat-treated object; a circulating pipe 49 that is arranged in a standing posture, and circulates the object between the outlet 27 of the treatment container 11 and the cooling unit 3; and the valve 50 that has the fluid seal, and is provided in the circulating pipe 49.