(EN) An electric current detector has, provided within an exterior case (1): an annular core (2) which has a magnetic gap (G); and a Hall element (41) which is located within the magnetic gap of the core (2) and detects the magnitude of an electric current passing through the core (2). The core (2) has a core component formed integrally therewith. The core component is configured by forming a mold resin section (3) on one or more portions of the core (2) so as to be disposed along the magnetic path of the core (2), and the mold resin section (3) covers the surface of the core (2) for a part of the entire length thereof along the magnetic path. The core component is affixed to the inside of the exterior case (1) with the surface of the mold resin section (3) in contact with the inner surface of the exterior case (1).