A container corner fitting provided at each right angle of a container body and connected with other parts of the container body includes a sealing device arranged thereon including a first flange of a predefined length provided on one of an inner side surface and a top or a bottom surface of the corner fitting. A second flange of a predefined length is provided on the other of the inner side surface and the top or the bottom surface of the corner fitting and aligned with the first flange. The seal gasket, provided with circumstance of the container gate, can depend on the first and second flanges while closing the gate, greatly improving container hermetic performance. The thickness of an upper or a lower horizontal container member can be reduced to approximate that of a top or a bottom container plate, obtaining the largest volume without inclining the bottom plate.