To provide a spiral element made of a material containing carbon fiber, by heating a starting material having carbon fiber and embedded in a thermoplastic embedding material till the embedding material is softened, winding it around a shaft while forming it into a spiral, and fixing the shape of the spiral while removing the embedding material.

A band-like carbon-fiber/resin composite material 3 is supplied to a rotating shaft 4 and spirally wound therearound while a winding area continuously moves sideward to form a spiral shape. In the winding area, the resin of the carbon-fiber/resin composite material 3 is softened by a hot-air blower 5, plastic thermal deformation becomes possible, and winding into a spiral shape can be performed. The carbon-fiber/resin composite material 3 is cooled down on the shaft 4, then glow-treatment at about 1,000°C is performed in a nitrogen atmosphere to gasify the resin or decompose it into gaseous constituents, thus a spiral carbon band is obtained. The surface area of this carbon band is larger than the surface area of a cylindrical heating element of the same length and therefore offers a higher radiation output.