An acoustic wave device includes: a piezoelectric substrate; an IDT that is formed on the piezoelectric substrate and includes a pair of comb-shaped electrodes facing each other, each of the pair of comb-shaped electrodes including an grating electrode that excites an acoustic wave and a bus bar to which the grating electrode is connected; and reforming regions that are located only inside the piezoelectric substrate and arranged at intervals under the IDT, and in which a material of the piezoelectric substrate is reformed.