PURPOSE: To provide a heating device which can heat an annular heating area quickly.

CONSTITUTION: A laser beam transmitting optical fiber 14 which is connected with a laser beam source on one end side and transmits laser beam from this laser beam source, a converging optical system 12 which converges laser beam connected with the other end side of this laser beam transmitting optical fiber 14 and emits it from the other end side of the laser beam transmitting optical fiber 14, a convex conical mirror 19 which is opposite coaxially to this converging optical system 12 and whose outer peripheral surface functions as a conical reflection surface and a concave conical mirror 21 which irradiates a part to be heated with annularly bent laser beam reflected by this convex conical mirror 19 and functions as a conical reflection surface through the inner peripheral surface are installed.