A resonator, a band-pass filter, and a duplexer are provided. In the resonator, a first electrode is formed of a nonmagnetic conductive material. A ferromagnetic fixed layer is disposed on the first electrode and has a magnetization direction which is fixed. A nonmagnetic conductive layer is disposed on the ferromagnetic fixed layer. A ferromagnetic free layer is disposed on the nonmagnetic conductive layer and has a magnetization direction which varies depending on an external magnetic field. A second electrode is disposed on the ferromagnetic free layer and comprises a nonmagnetic conductive material. The band-pass filter and the duplexer are configured using the resonator. The band-pass filter and the duplexer can operate in a high-frequency range and be miniaturized. The bandwidth of the band-pass filter and the duplexer can be adjusted and the band-pass filter and the duplexer can be formed in one body with an integrated circuit.