A filter includes a series-arm resonator located on a path that connects an input/output terminal (11m) with an input/output terminal (11n), and a first parallel-arm resonant circuit connected between a node, which is located on the path, and ground. The first parallel-arm resonant circuit includes a parallel-arm resonator, and a pair of a capacitor and a switch connected in parallel with each other and in series with the parallel-arm resonator between the parallel-arm resonator and ground. An interconnect line (a1) is connected to the input/output terminal (11m), and an interconnect line (a2) is connected to the input/output terminal. The parallel-arm resonator and the switch are connected by an interconnect line (a3). The interconnect line (a3) has a characteristic impedance lower than a characteristic impedance of the interconnect line (a1) or a characteristic impedance of the interconnect line (a2).