A band pass filter configured by a planar structure circuit, includes resonators of distribution constant circuit type, transmission line paths coupling the resonators and excitation lines arranged at input/output sides. The transmission line path is provided with line path portions coupling the resonators or the resonator and the excitation line. The line path portion have a length which is (1+2m)/4-fold (m: natural number) of a wavelength corresponding to a center frequency of the frequency band, and each coupling part between the resonators and the line portion has a length substantially determined as a 1/4 wavelength.