An elastic wave resonator includes series divided resonators on a piezoelectric substrate, first and second outer busbars, a first interstage busbar, first to fourth electrode fingers and first and second dummy electrode fingers. Third dummy electrode fingers are not provided at at least one of a side where the second electrode fingers are provided and a side where the third electrode fingers are provided or third dummy electrode fingers having a length smaller than lengths of the first and second dummy electrode fingers are provided at at least one of a side where the second electrode fingers are provided and a side where the third electrode fingers are provided. The third electrode fingers are arranged on an extension to which the second electrode fingers extend.

An acoustic wave device includes a first acoustic wave filter including a first piezoelectric substrate and first resonators on the first piezoelectric substrate, and a second acoustic wave filter including a second piezoelectric substrate and second resonators on the second piezoelectric substrate. The first and second resonators are opposed to each other with a gap therebetween. The first and second resonators each include a heat-generation resonator in which a heat generation range has a highest temperature at a time of signal application. The heat generation ranges of the heat-generation resonators do not overlap each other in plan view.