A transfer chamber is partitioned into a second chamber in which a transfer robot moving through an opening portion which can be opened/closed by a door is arranged, and a minute first chamber which serves as a FIMS system and includes a door capable of retaining a lid of a pod. The second chamber maintains a state in which an inert gas constantly circulates owing to minute nitrogen while having a pressure higher than that inside the first chamber. The first chamber is normally sealed while an oxide gas is suppressed in advance. In addition, at a time of transferring wafers, a partial pressure of the oxide gas is lowered with use of a downflow which is caused by the inert gas. Further, the first chamber and the second chamber are communicated with each other after a level of the partial pressure is confirmed with use of an oxygen level meter. As described above, an existing amount of the oxide gas is reduced in the so-called transfer chamber in semiconductor processing equipment in which the FIMS system is secured.