There are provided a heater unit and a battery structure with heater, which are capable of heating the battery structure appropriately and preventing a heater (part or whole of the heater) itself from excessively increasing in temperature. A first heater unit is provided with a first sheet heater, a first holding member holding it, and a first sheet placed between a lower surface of a first heater and the first holding member in such a manner as to be deformable in at least a direction of thickness of the first heater. The first heater is deformed when the first heater unit is fixed to the battery pack 50, thereby pressing the lower surface of the first heater to bring an upper surface of the first heater into close contact with an outer surface (a surface to be heated) of a spaced part of the battery pack.