To prevent disconnection and improve durability by constituting a heater with a transparent synthetic-resin-made cylindrical base material, a metallic heating strand placed on the outer side surface, and insulation layer covering its outer side.

Material of a cylindrical base material is transparent and durable to heating of a cylindrical heater, polycarbonate or others are preferable. Its transparency is extent in which a signal lamp installed inside the cylindrical heater can be seen through. A metallic heating strand is formed by stranding plural metallic heating wires, space occurs between metallic heating wires, and apparent cross section enlarges. Even when the cylindrical base material expands due to rapid temperature rising, tensile stress due to expansion is moderated and disconnection does not occur. As the metallic heating wires, nickel chromium wires or others are used. Wiring of the metallic heating wires around the cylindrical base material is preferably to spirally wind them on the outer side of the cylindrical base material. As material of an insulating layer, polycarbonate or others are preferable.