An antenna comprising a magnetic main-path member comprising a coil wound around a magnetic core, and a magnetic sub-path member magnetically connected to the magnetic core for constituting a substantially closed magnetic path with the magnetic main-path member, the antenna meeting the relation of (S/N).sub.1>(S/N).sub.0, wherein (S/N).sub.1 is a ratio of a signal voltage S obtained from the coil to a noise voltage N in this antenna, and (S/N).sub.0 is a ratio of a signal voltage S to a noise voltage N in an antenna having the same structure except for having no magnetic sub-path member.