In an electric current detector according to the present invention, an annular core 2 having a magnetic gap G and a Hall element 41 which is located in the magnetic gap of the core 2 and detects a magnitude of an electric current passing through the core 2 are arranged in an outer case 1. Here, in the core 2, a mold resin portion 3 which covers a surface of the core 2 over part of an overall length along a magnetic path thereof is molded at one or a plurality of portions along the magnetic path to configure an integral core component, the core component being fixed into the outer case 1 in a state where a surface of the mold resin portion 3 makes contact with an inner surface of the outer case 1.