When a current flowing in a series circuit including an equivalent resistance, an equivalent inductor, and an equivalent capacitance in an electric equivalent circuit of a specific resonator in each filter is defined as an acoustic path current, under conditions that a phase of an acoustic path current of a first transmission filter at a side of a common terminal at a frequency within a first transmission band is represented as θ1Tx, a phase of an acoustic path current of the first transmission filter at the side of the common terminal at a frequency within a second transmission band is represented as θ2Tx, a phase of an acoustic path current of a first reception filter at the side of the common terminal at a frequency within the first transmission band is represented as θ1Rx, and a phase of an acoustic path current of the first reception filter at the side of the common terminal at a frequency within the second transmission band is represented as θ2Rx, a multiplexer satisfies a first condition: |(2·θ1Tx−θ2Tx)−(2·θ1Rx−θ2Rx)|=180°±90°, or a second condition: |(2·θ2Tx−θ1Tx)−(2·θ2Rx−θ1Rx)|=180°±90°.