A heater unit having high in-plane temperature uniformity is provided. A heater unit includes a first heater part, a second heater part controlled independently of the first heater part, a base arranged with a groove in a region between the first heater part and the second heater part, and a cover part arranged at an opening end of the groove and providing a closed space with the groove. In addition, an insulating layer covering the first heater part and the second heater part, and an electrostatic chuck attached to the base via the insulating layer may be further included. In addition, the closed space provided by the cover part and the groove may be a vacuum.