An acoustic wave element includes a piezoelectric substrate, an excitation electrode configured to excite and output a main acoustic wave on the piezoelectric substrate, a receiving electrode configured to receive the main acoustic wave, a propagation path configured to allow the main acoustic wave to propagate along the piezoelectric substrate between the excitation electrode and the receiving electrode, and a sensing portion configured to react to an object substance. The propagation path is configured to allow the main acoustic wave to pass plural times through the sensing portion along the propagation path. This acoustic wave element has high sensitivity to the object substance.