Load port apparatus and method of mounting container

A load port apparatus includes a mount member, a purge nozzle, and a plurality of pins. The mount member mounts a container. The nozzle introduces a cleaning gas into the container mounted on the mount member via a purge port disposed on a bottom of the container. The pins support the container from below by each contacting with a predetermined position of the bottom of the container. The pins are relatively vertically movable to the mount member between a first position and a second position where an upper tip of each of the pins is located lower than that at the first position. The upper tip of each of the pins at the first position contacts with the predetermined position of the container. The upper tip of each of the pins at the second position contacts with the predetermined position of the container.