In a filter device 10 constituted by circuit elements formed on a single substrate 11, the circuit elements includes a first
wing section 14 formed between an input
signal electrode 12 and an output
signal electrode 13, first resonators 15a, 15b, 15c located in the first wiring section 14 and having a predetermined
resonance frequency, second wiring sections 17a, 17b, 17c, 17d formed between the first wiring section 14 and a ground
electrode 16, second resonators 18a, 18b, 18c, 18d located in the second wiring sections 17a, 17b, 17c, 17d and having an anti-
resonance frequency forming a pass-band with the predetermined
resonance frequency of the first resonators 15a, 15b, 15c. An effective electric and mechanical
coupling factor of the second
resonator 18a is different from those of the other resonators 15a, 15b, 15c, 18b, 18c, 18d.