A superconductive coil assembly has a bobbin, a coil provided such that a superconductive wire is wound several times around the bobbin, and a pair of heat transfer plates installed to cover the opposite sides of the bobbin and the coil. The heat transfer plate is made of metal material with high thermal conductivity, such as copper or aluminum, and a portion thereof abutted upon the side of the coil is coated with electric insulating material. If adapted to a generator, an electric motor, and so on, the plurality of superconductive coil assemblies is used while being overlapped. In this case, a connection recess is provided to at least one heat transfer plate to enable a portion of the side of the coil to be exposed outside, in order for electrical connection with another superconductive coil assembly. By the construction of the superconductive coil assembly, a heat transfer path between the cooling source and the superconductive coil is diversified by the heat transfer plate, thereby shortening a cooling time of the superconductive coil as well as improving cryogenic operation stability. Further, the heat transfer plate protects the side of the superconductive coil so that even when the superconductive coil is applied to the inside of the rotor of a generator or an electric motor, and operates under the centrifugal force, it can operate stably and continuously.