To achieve rapid and accurate positioning, by setting an interferometer mirror to a hollow structure where both edges in a longitudinal direction are open edges.

A wafer to be exposed to light is placed at a top stage 5, a drive signal is given from an external controller to an XY stage, and the wafer is driven to a specific position. Deviation for the target position of the wafer in the direction of X, Y, and θ is calculated by the external controller based on the output of a laser measurement system, and is fed back to the drive part of the XY stage, and the wafer is controlled to be positioned at a specific position. Then, reflection mirrors 23c and 23d with hollow holes 22c and 22d are used to reduce mass of a mirror itself, increase characteristic vibration frequency of the bending direction and the twisting direction or the like of the reflection mirror itself, and improve positioning control accuracy.