A field-effect type superconducting device includes a channel layer (2). The channel layer includes Bi-based oxide compound containing Cu. A source electrode (5) contacts the channel layer. A drain electrode (6) contacts the channel layer. A gate insulating film (3) made of insulating material extends on on the channel layer. A gate electrode (4) extends on the gate insulating film. Also disclosed is a superconducting device having a control electrode (14) extending on the insulating film (3) and having a constricted portion (50B).
