To provide a mirror frame apparatus which can easily adjust the inclination of an optical axis and the position of the optical axis, and has a simple adjustment mechanism.

The lens barrel 10 in which the mirror flame apparatus permitting the adjustment of optical axis is incorporated, has a rotation frame 2 which can be advanced or retreated corresponding to the fixed frame 1, a rotation frame 3, a first group frame 4, etc. The first group frame 4 is mainly composed of an outer frame part 4a and an inner frame part 4b which is connected with the outer frame part through a connecting part, and holds the first group lens 51. An eccentric pin 31, etc., for tilt adjustment and a adjustment screw 35, etc., for shift adjustment are arranged on the outer periphery of the inner frame part 4b. The inclination or the position of the inner frame part 4b is changed by performing rotation adjustment of the eccentric pin 31, etc., or the adjustment screw 35, etc., and deforming the connecting part. Thereby, the inclination or the position of the optical axis of the first group lens 51 can be adjusted.