PURPOSE: To facilitate a change of a heater shape and prevent exfoliation of a far infrared-ray radiating material at the time of using the heater by providing a process of partially coating the heater surface with a far infrared-ray radiating material before a bending process of the heater shape.

CONSTITUTION: The surface of a sheath heater 3 is flame-coated with far infrared-ray ceramics molten particles 2 excepting the part masked by a masking material 4 by scanning with a flame-coating gun 1 and rotation having the center line of the sheath heater 3 as a rotation axis. By performing a bending process of the heater part not coated with the far infrared-ray radiating ceramics 5, a desired heater shape can be obtained by curved shaping or the like. Further, the ceramics 5 can easily be coated to uniform thickness at the time of coating the surface of the heater 3 with far infrared-ray radiating ceramics 5, since the heater 3 is of a rotatable simple cylindrical form.