A SAW device comprises a single crystal piezo-electric strate (made, for example, of LiTaO3 or LiNbO3), and an interdigital transducer (IDT) formed of a material mainly containing Al and disposed on the piezo-electric substrate. The piezo-electric strate contains an additive (for example, Fe, Mn, Cu, Ti), and an orientation rotated by an angle in a range of 42° to 48° (more preferably 46°±0.3°) from a Y-axis toward a Z-axis about an X-axis. The IDT presents a normalized thickness h / λ (h: thickness of electrode, and λ: spacing between digits of the IDT) of 7% to 11%. A more appropriate substrate cut angle can be shown for the SAW device which employs a piezo-electric substrate containing an additive, to improve the electric characteristics thereof.