To prevent the contamination of a water being transferred to a positioning stage, etc., in a low-pressure chamber.

In a low-pressure chamber 1 a down-flow of an atmosphere gas blown out of blowout holes 26 occurs, against which a wafer W held with a substrate holder 13 of a substrate transfer 10 is covered with a cover 12, and a local flow of gas blown via a blowout part 11 out of a branch feed line 22 branched from a circulation feed line 21 of the low-pressure chamber 1 is made to flow in parallel with the wafer W, thereby preventing the wafer W from being contaminated with particles which falls with the down-flow.