An aligner in which light absorbing substances can be removed appropriately from the space between a projection optical system and a substrate without having any effect on the peripheral apparatus. The aligner has a gas supply port for supplying an energy-beam-permeable gas to the space between the projection optical system and the substrate, and an exhaust port provided on the outside of the gas supply port while being directed toward the space and discharging a gas containing the permeable gas from the space at a rate higher than the supply rate of the permeable gas.