There is provided a resonance circuit using piezoelectric vibrator such as a quartz resonator, a coil, a capacitor, or an element equivalent to them in combination. When two resonance circuits having different resonance frequencies are combined, it is possible to configure an oscillation circuit and a filter capable of freely adjusting the frequency characteristic by utilizing the phenomenon that by changing the excitation current or voltage of the respective resonance circuits independently from each other, antiresonance frequency of the entire composite resonance circuit can be changed.