An acoustic wave device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode, a reflector electrode, and a dummy electrode. The IDT electrode includes electrode fingers extending in a predetermined direction. The reflector electrode faces the IDT electrode across a gap. The dummy electrode is situated on a straight line extending in the predetermined direction through the gap. At least one of the distance between the dummy electrode and the IDT electrode and the distance between the dummy electrode and the reflector electrode is larger than the distance between the IDT electrode and the reflector electrode. This acoustic wave device prevents a short circuit between the IDT electrode and the reflector electrode, thereby avoiding a decrease in its yield.