is possible to reliably separate the alignment region a and the exposure region e even when it is a wafer stage system 100 with a complex shape so leakage of gas g is almost entirely eliminated also as in the case in which a shielding plate 67 is provided there is an advantage in that the shape and the like of the wafer stage system 100 is never restricted in addition a plurality of supply ports 63 and exhaust ports 64 may be provided for example two exhaust ports 64 are provided as in fig6 a and two pairs of supply port 63 and exhaust port 64 are provided as in fig6 b and a flow path by which the gas g within the chamber 61 flows from the alignment region a toward the exposure region e is formed in this case as well it is preferable to provide a shielding plate 67 or an air curtain 68 between the alignment region a and the exposure region e in the configuration of fig6 b a supply port that supplies gas to the exposure region e and a supply port that supplies gas to the measurement region a are individually provided in the respective regions so they may be set so that the properties flow amount humidity temperature constituents and the concentration thereof and the like of the gas supplied from the respective supply ports are mutually different in addition in the embodiment discussed above an explanation was given with respect to eliminating the effects of humidity on laser interferometers 192 and 194 which measure the position of the wafer.