Electrical connection of superconducting lines can be achieved by using a low-melting point metal, by mechanical contact of superconducting lines or by welding. According to these methods, however, critical current and critical magnetic field at the connection point are low, and stable connection in a superconducting state has been difficult. The present invention solves these problems and provides a structure and method for connecting superconducting lines (1a, 1b). The present invention provides high-performance, high-stability connection of superconducting lines through magnesium diboride (MgB 2 ) powder (2) arranged between superconducting lines (1a, 1b).