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 pass band is represented as θ1Tx1, 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 pass band is represented as θ2Tx1, a phase of an acoustic path current of a second transmission filter at the side of the common terminal at a frequency within the first pass band is represented as θ1Tx2, and a phase of an acoustic path current of the second transmission filter at the side of the common terminal at a frequency within the second pass band is represented as θ2Tx2, a multiplexer satisfies a first condition: |(2·θ1Tx1−θ2Tx1)−(2·θ1Tx2−θ2Tx2)|=180°±90°, or a second condition: |(2·θ2Tx1−θ1Tx1)−(2·θ2Tx2−θ1Tx2)|=180°±90°.