Reflecting mirror unit

A reflecting mirror unit characterized by comprising

• a unit main portion having
• a mirror,
• mirror holding means for holding the periphery of the mirror, in which an outer circumferential portion perpendicular to a reflection surface of the mirror is shaped like a circular arc in cross section,
• a first carrier that is in contact with a part of the outer circumferential portion on the mirror reflection surface side of the mirror holding means at a part of an inner conical surface of the first carrier,
• a second carrier that is opposed via the mirror holding means to the first carrier, and is in contact with a part of the outer circumferential portion on the mirror back face side of the mirror holding means at a part of an inner conical surface of the second carrier, and
• pressure securing means for pressing the first carrier and the second carrier against the mirror holding means;
• and
• mirror adjusting means, which is provided to be separable from the unit main portion, for adjusting a reflection direction of the mirror in a state where the mirror holding means and the first carrier are contacted.