An acoustic wave device includes a piezoelectric substrate, a comb-shaped electrode formed on the piezoelectric substrate and configured to excite a Rayleigh wave as a main acoustic wave, a first dielectric film formed above the piezoelectric substrate to cover the comb-shaped electrode, and a second dielectric film having a portion provided between electrode fingers of the comb-shaped electrode and a portion provided above the comb-shaped electrode. The portion provided between the electrode fingers is provided between the piezoelectric substrate and the first dielectric film. The portion provided above the comb-shaped electrode is provided between the comb-shaped electrode and the first dielectric film. A speed of a transverse wave propagating through the first dielectric film is lower than a speed of the Rayleigh wave excited by the comb-shaped electrode. A speed of a transverse wave propagating through the second dielectric film is higher than the speed of Rayleigh wave excited by the comb-shaped electrode.