In this invention, a movable body movable in forward and backward directions and a connector fixed to an opener-side door are connected with each other by link members so as to constitute a parallel link mechanism, such that they can be angularly displaced relative to each other. Link member angular displacement means controls the angular displacement of each link member relative to the movable body to be in a predetermined angular position, corresponding to the position of the movable body along the forward and backward directions. Reciprocation of the movable body in the forward and backward directions by movable body drive means moves the opener-side door in the forward and backward directions as well as in the upward and downward directions, thereby opening an opener-side opening. Since the movable body is moved only in the forward and backward directions, and necessity of moving and guiding the movable body in the upward and downward directions can be eliminated, the substrate container opener can be downsized, and a space provided below a FOUP supporting portion can be utilized effectively.