A first filter of a multiplexer has a ladder filter structure including a plurality of series resonators and a plurality of parallel resonators. Each resonator is an acoustic wave resonator that includes an IDT electrode including a pair of comb-shaped electrodes. A portion having a unit area, in a plan view of a substrate on which the resonators are provided, has a larger weight in at least one of the IDT electrode of the series resonator that is closest to the common terminal, among the series resonator, and the IDT electrode of the parallel resonator that is closest to the common terminal than in the IDT electrode of each of the remainder of the plurality of acoustic wave resonators.