A magnetic core includes a first core having a predetermined magnetic permeability and a second core formed of the same material as the first core. The second core forms a closed magnetic circuit together with the first core. The second core is configured to radiate heat through a heat radiating unit. At least one of the first core and the second core is configured to be wound with a coil. The magnetic core includes a third core that is arranged between the first core and the second core and has a lower magnetic permeability than the first core.