To prevent the degradation in throughput even if the frequencies of exchanging reticles are high.

Reticle alignment microscopes AS1A, AS1B are internally provided with index marks 28A, 28b and the lower part of the reticle 5 is provided with shutters 10A, 10B for shielding the illumination light for alignment. The mispositioning quantity of the first sheet of the reticle 5 with respect to a reference mark member 6 is determined by the reticle alignment microscopes AS1A, AS1B and the base line quantity of an alignment sensor AS2 is determined. The differences between the positions at the pattern centers of the reticle 5 and the central positions of the index marks 28A, 28B are then stored. For the second and subsequent reticles, the operation on the reticle side and the operation on the wafer side are executed in parallel in the state of closing the shutters 10A, 10B. In such a case, the differences between the position of the pattern centers of the reticles and the central positions of the index marks are determined by the reticle alignment microscopes AS1A, AS1B and the already determined base line quantity is corrected by these differences.