A mirror adjustment mechanism including a first reflection mirror rotatable around a rotation shaft, and a second reflection mirror rotatably provided on the first reflection mirror. One of the ends of the rotation shaft of the first mirror is allowed to move in the direction of the surface of the first mirror. By this movement, it is possible to adjust the direction of the reflecting light on the second mirror without substantially affecting the direction of the reflecting light on the first mirror. For example, the present invention can be applied to the adjustment of a sub-mirror rotatably mounted on a main mirror of a single-lens reflex camera.