The present invention relates to a superconducting power transforming apparatus. The superconducting power transforming apparatus according to the present invention comprises a transformer housing having a transforming cable passing hole and filled with a liquid cooling means; a superconducting transformer housed in the transformer housing in a state that the superconducting transformer is immersed in the liquid cooling means; a tap changer housing having a tap changing cable passing hole and vacuum-sealed from outside; a power tap changer housed in the vacuum tap changer housing; and a cable linking pipe vacuum-sealed from the transformer housing and the tap changer housing, and linking the transforming cable passing hole with the tap changing passing hole in order that a transformer winding tap cable connecting the superconducting transformer and the power tap changer passes through. Consequently, it is possible to guarantee stable operation of a superconducting transformer which works at an extremely low temperature and a power tap changer as like On-Load Tap Changer which works at low temperature.