There is disclosed an acoustic wave apparatus, constructed in such a manner that a surface rotated in the range of 34° to 41° from a crystal Y axis around the crystal X axis of lithium tantalate is set as the surface of a substrate, a standardized electrode thickness (h/&lgr;) obtained by standardizing a thickness h of an electrode finger constituting at least a part of an interdigital transducer by a wavelength &lgr; of a surface acoustic wave is set to the range of 0.01 to 0.05, and a duty ratio (w/p) of the electrode finger decided based on a width w and an arraying cycle p of the electrode finger is set to the value ranging from 0.6 to just below 1.0.