AbstractThe Module Coil (TOKI-MC) was designed and fabricated in order to study the mechanical properties of the helical coils of the Large Helical Device (LHD). The magnetic field inside the winding of TOKI-MC has been calculated assuming that the current density is uniform in the winding and the cross section perpendicular to the current is rectangular. The maximum magnetic field is 7.6 T and the electromagnetic force per unit length is about 11 MN/m. Stress analysis has been performed by using the finite element method in order to investigate the deformation behavior of the winding. The twisted solenoid winding tends to become a normal solenoid one and then the stress to the coil case is up to 35 MPa. The possibility of generation of a normal zone may be suggested.