An acoustic wave device is an end surface reflection-type acoustic wave device and includes a substantially rectangular-parallelepiped composite substrate in which a piezoelectric substrate and a supporting substrate are joined together, with a pair of IDT electrodes provided on the substrate in such a manner as to be intercalated with each other. A chipping size in a first side face of the substrate is 1/10 of a wavelength λ of an acoustic wave or smaller, the face extending orthogonally to a direction of acoustic-wave propagation. A chipping size in a second side face of the substrate is larger than the chipping size in the face and is, for example, ½ of the wavelength λ or larger and 50 times the wavelength λ or smaller, the face extending in the direction of acoustic-wave propagation.