Provided are a door opening/closing system which prevents the entry of atmospheric air into a front-opening unified pod (FOUP) and an equipment front end module (EFEM) when the FOUP and the EFEM are placed in communication with each other, and a load port equipped with the door opening/closing system. The door opening/closing system is provided with: a base which constitutes a part of a wall isolating a conveyance space from an external space, an opening portion provided in the base; a door which is capable of opening and closing 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 which is constituted by the base, the first seal member, the second seal member, a lid member, and the door when the container is in a 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 88 which evacuates the sealed space.