To provide an antenna whose center frequency can be easily and quickly changed/adjusted.

An antenna 1 comprises: a magnetic body 2 disposed on at least part of a conductor 3 for the antenna; a permanent magnet 6 for applying a DC magnetic field to the magnetic body 2; and a coil 7 for remagnetization disposed around the permanent magnet 6. A power supply unit 8 for supplying a current for remagnetization is connected to the coil 7. A magnetization control unit 9, which controls the power supply unit 8 to remagnetize the permanent magnet 6 so that the DC magnetic field has a predetermined magnetic field strength, is connected to the power supply unit 8.