A door opening/closing system includes: a base as part of a wall isolating a conveyance space from an external space; an opening portion provided in the base; a door configured to open/close the opening portion; a first seal member which seals a gap between the base and a container; a second seal member which seals a gap between the base and the door; a sealed space constituted by the base, the first and second seal members, a lid member, and the door when the container state of contact with the opening portion with the first seal member therebetween; a first gas injection unit which injects gas into the sealed space; and a second gas discharge unit which evacuates the sealed space. The door opening/closing system prevents entry of atmospheric air into a front-opening unified pod and an equipment front end module when placed in communication.