Abstract: A surface acoustic wave device comprises a piezoelectric substrate of lithium tetraborate single crystal, and a metal film formed on the surface of the piezoelectric substrate for exciting, receiving, reflecting and/or propagating surface acoustic waves, the metal film being so formed that a cut angle of the surface of the piezoelectric substrate and propagation direction of the surface acoustic wave are an Eulerian angle representation of (0.degree.-45.degree., 30.degree.-90.degree., 40.degree.-90.degree.) and directions equivalent thereto, the surface acoustic wave having higher propagation velocity than Rayleigh waves and leaky waves, and a characteristic of radiating part of energy of the surface acoustic wave into the piezoelectric surface while propagating.