Provided is an elastic wave apparatus that uses an S0 mode of a plate wave and with which variations tend not to occur in the speed of sound or frequency characteristics even if the thickness of an electrode film changes. In the elastic wave apparatus 1: an IDT electrode 6 having a plurality of electrode fingers is provided on a first main surface 5a of a piezoelectric thin film 5; a conductive layer 8 is provided on a second main surface 5b of the piezoelectric thin film 5; an elastic wave propagating through the piezoelectric thin film 5 is an S0 mode of a plate wave; and a portion of the piezoelectric thin film 5 in a region under a space between the electrode fingers of the IDT electrode 6 changes more greatly than the electrode fingers and portions of the piezoelectric thin film 5 in the regions under the electrode fingers.
