PURPOSE: To make irradiating pattern within a face including an optical axis symmetrical by constituting a main reflection mirror with a parabola reflection mirror and constituting a sub-reflection mirror with a dielectric support fixed to the main reflection mirror.

CONSTITUTION: The main reflection mirror 22 is a reflection mirror of a parabolid of revolution, and the sub-reflection mirror 21 consists of the dielectric support fixed to the main reflection mirror 22 and also a vapor-deposited metallic face is formed to a focal point of the main reflection mirror 22. In the sub- reflection miror 21, an end face 23-1 of a dielectric substance rod 23 is shaped in the form of mirror surface and a vapor-deposited metallic mirror surface 24 is provided on the end face 23-1. In this case, it is possible for a support dielectric substance 25 to have the rod form inside or to be bored. The sub-reflection mirror and the supporting rod are incorporated so as to constitute the sub-reflection mirror 21 thereby making the irradiation pattern within the face including the optical axis symmetrical.