AbstractA calculation of the electromagnetic forces was carried out to design the supporting structure and the coil package. LHD has one pair of helical coils and three pairs of poloidal coils, all of which are superconducting coils. Because of the large electromagnetic force, the helical coils are fixed to a cylindrical supporting structure that is called the shell support. From the comparison between three types of methods to support the poloidal coils is found that the most suitable is that with the poloidal coils fixed firmly to the shell support in all directions. When considering the rigidity of the poloidal coils, the maximum stress of the shell support is smallest with this type. The forces on the electrical insulators of the helical coils are estimated by calculating the electromagnetic forces on each conductor and summing them. The maximum loads on the insulators between turns and between layers are 159 and 116 MPa, respectively. They occur in the center area of the coil cross section.