An acoustic wave resonator includes: a piezoelectric substrate; and an IDT that is located on the piezoelectric substrate and includes comb-shaped electrodes facing each other, each of the comb-shaped electrodes having grating electrode and a bus bar connected to the grating electrodes, a duty ratio of grating electrodes of the comb-shaped electrodes in a center region of an overlap region differing from a duty ratio of grating electrodes of the comb-shaped electrodes in an edge region of the overlap region in an arrangement direction of the grating electrodes, the grating electrodes of each of the comb-shaped electrodes overlapping with the grating electrodes of the other in the overlap region, a grating electrode of a first one of the comb-shaped electrodes in the center region having a different width from a grating electrode of a second one of the comb-shaped electrodes in the center region.