The KSTAR vacuum vessel consists of double-wall configuration with major ports, reinforcing ribs and supporting structures. The vacuum vessel structure supports all in-vessel structures. The electromagnetic loads on the plasma facing components induced during plasma disruptions would be transferred to the vessel through the supporting structure and produce a large localized stress on the interface between the vessel and the supporting structure. Due to the element limitation of load calculation code, a simplified supporting structure model was defined to obtain the electromagnetic loads on the plasma facing components. A new transferring method of these loads to the interface area was developed. In this paper the electromagnetic loads on the in-vessel components were calculated and stress analyses were performed to help design the interface area based on the equivalent forces estimated using the developed EM load transferring method.