A magnetic assembly includes a mounting substrate and a magnetic element mounted on the mounting substrate. The magnetic element includes a drum core provided with a flange portion at each end of a winding shaft, a coil wound on the winding shaft, and a shield core engaged with the drum core, the shield core including an engagement portion having a shape that corresponds to the shape of a portion of the outer circumference of at least one of the flange portions so that the engagement portion mates with the at least one flange portion.