A SAW resonator disposed with an IDT electrode and reflector electrodes is formed on the surface of a piezoelectric substrate (11). Three pieces of the SAW resonator form an acoustic coupling by being disposed close to each other, electrode fingers comprising the IDT electrode (13a) in the center are all grounded, and IDT electrode fingers are electrically independent on the side to be connected to input-output terminals of the IDT electrodes (12a, 14a) disposed outside. As a result, three excitation modes having different propagation frequencies are generated which are used to attain a broad band SAW resonator filter. When these three pairs of the IDT electrode are electrically independent, a balanced input-output can be achieved, and excellent out-of-band rejection characteristics can be obtained.