A magnetic core includes a first core and a second core, which is formed of material having a lower magnetic permeability and a higher saturation magnetic flux density than those of the first core. The second core forms a closed magnetic path together with the first core. The second core has a distal surface held in contact with the first core. The area of the distal surface is larger than the smallest cross-sectional area of the second core in a direction perpendicular to the flow direction of magnetic flux in the closed magnetic path.