A duplexer with a reduced filter loss is provided. The duplexer includes two or more filters F1 and F2 that are connected to a common terminal and that have different passbands. At least one of the filters F1 and F2 includes a plurality of series resonators S1 to Sn connected in series to a path between an input terminal and an output terminal of the filter, and parallel resonators P1 to Pm connected in parallel to the above-mentioned path. An inductance L1 is connected in parallel to at least one of the series resonators, and the series resonator S1 having the inductance L1 connected in parallel thereto is divided into a plurality of resonators S11 to S13 connected in series.