An acoustic wave device capable of exhibiting good characteristics for a prolonged period of time and a method of manufacturing an acoustic wave device are provided. An acoustic wave device of the invention includes a piezoelectric body layer having piezoelectricity and one surface, a pair of electrodes for, when electrified, inducing acoustic vibration in the piezoelectric body layer, the electrodes arranged on the one surface of the piezoelectric body layer, and a silicon dioxide layer provided in contact with the piezoelectric body layer and/or the electrodes, the silicon dioxide layer composed of silicon dioxide as its major component, wherein the silicon dioxide layer is formed by performing sputtering with a silicon dioxide target in an atmosphere of an oxygen flow rate ratio of 60% or more.