A signal switching device including a plurality of transmission paths connected to an input path, the signal switching device outputting a signal from the input path through one of the transmission paths, including a first variable impedance unit connected to a first transmission path, the first variable impedance unit including a first section formed from a superconducting material, the first section being set to a non-superconducting state when the signal is to be output through a second transmission path, the first section including a portion of a predetermined length at an input end, the portion having an area of a cross section less than an area of a cross section of the first section at an output end.