A multiplexer includes a common terminal, a first band pass filter that is connected to the common terminal and has a first pass band, and a second band pass filter that is connected to the common terminal and has a second pass band located at higher frequencies than the first pass band. The first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, and an IDT electrode provided on the piezoelectric body. The piezoelectric body is made of lithium niobate. The acoustic wave device utilizes Rayleigh waves.