The main problem to manufacture the superconducting helical coil for the heliotron fusion reactor is to develop an easily demountable joint of superconductor. We have designed an “Inserting Method” joint for this purpose and measured the contact resistance at liquid helium temperature and the tensile strength of the joint at liquid nitrogen temperature. We have confirmed the possibility to apply the “Inserting Method” joint to the superconducting demountable helical coil.