PURPOSE: To provide an external light mirror furnace capable of extremely lowering light emitted to an external part from a focal point for conversely introducing light from the external part and thus improving heating efficiency.

CONSTITUTION: This external light mirror furnace comprises a rotary elliptical face mirror 12 having two focal points F1 and F2, an external light introducing device 14 for introducing and converging external light to one focal point F1 and a light receiving member 16 arranged at the position of the focal point F1. At the other focal point F2, a member 20 to be heated is arranged. The light from the light receiving member 16 is reflected on the inner surface of the rotary elliptical face mirror and converged to the member to be heated, go that the member to be heated is heated. Light or radiation heat emitted from the member heated to high temperature is reflected on the inner surface of the rotary elliptical face mirror and reaches one focal point where the light receiving member is reheated.