A composite resonance circuit is provided of which the resonance frequency is variable over a wide frequency range without changing the circuit constant of a non-resonant element having no resonance frequency. The composite resonance circuit comprises an input terminal; a resonance unit having first and second ports and quasi-resonating in response to AC signals respectively supplied to these ports; and phase shift circuits that perform different phase shifts on an AC signal supplied to the input terminal and supply first and second shifted signals subjected to the phase shift respectively to the first and second ports. The resonance unit is an impedance circuit that has at least four input terminals forming the first and second ports and that generates a quasi-resonant peak current under non-zero reactance in response to the first and second shifted signals coming in via the first and second ports. The quasi-resonant peak current is variable according to the frequency and phase shift quantities of the AC signals. Namely, the resonance frequency can be made to be variable.