To provide a heater unit and a heat treatment device capable of reducing heat loss in a connection with a power feed terminal of a heating element.

The heater unit HUa includes the heating element Ha, the power feed terminal 20, and an intermediate 40. The power feed terminal 20 is composed of a metal material and supplies electric power to the heating element Ha. The intermediate 40 is composed of a carbon based material, and connected between the heating element Ha and the power feed terminal 20. The intermediate 40 has a function of heat-insulation between the heating element Ha and the power feed terminal 20. For this reason, even when the power feed terminal 20 is cooled and operated, it becomes possible to suppress heat loss of the heating element Ha. Accordingly, by the heater unit HUa, it becomes possible to prevent temperature reduction in the connection with the power feed terminal 20 of the heating element Ha, and improvement of heating uniformity is achieved.