An irreversible circuit element that can reduce manufacturing costs by preventing faults that lead to product defects includes a magnetic body, a magnetic body securing casing, and a magnet. The magnetic body securing casing is arranged so as to surround the magnetic body. The magnet is arranged on one side of the magnetic body. The magnetic body securing casing includes a first electrode on one casing main surface arranged on the one side, a second electrode on the other casing main surface arranged on the other side opposite to the one side, and a through-conductor that passes through the magnetic body securing casing and electrically connects the first electrode to the second electrode. The first electrode is connected to a first wiring arranged on the one side of the magnetic body.