To provide a small-sized inexpensive irreversible circuit element having a low height, without deteriorating the characteristics of an isolator and a circulartor.

An assembly is formed by arranging center conductors, whose one end is connected to a capacitor and whose other end is connected to ground are placed in crossing in an electrically isolated state on a magnetic material in a magnetic circuit configured, by placing a permanent magnet between an upper yoke and a lower yoke. The irreversible circuit element, having external terminals to which the center conductors are connected, is provided with a resin case that contains the assembly and the capacitor. The resin case and the lower yoke are integrally injection molded.