A first filter of a multiplexer includes a ladder filter structure with a plurality of series resonators and a plurality of parallel resonators. Each resonator is an acoustic wave resonator that includes an InterDigital Transducer (IDT) electrode including a pair of comb-shaped electrodes. A total number of reflection electrode fingers of the reflectors of at least one of the series resonator that is closest to the common terminal among the series resonators and the parallel resonator that is closest to the common terminal is smaller than a total number of reflection electrode fingers of the reflectors of each of a remainder of the resonators.