A magnetostrictive actuator includes: a driving unit composed of generally plate-like positive and negative magnetostrictive elements laminated in a direction of thickness, being arranged generally in parallel with a drive surface of a driven member; a driving coil for applying a magnetic field to the driving unit longitudinally, being arranged around an outer periphery of the driving unit; and a pair of bias magnets for applying a bias field to the driving unit longitudinally, being capable of transmitting a displacement of the driving unit to the driven member. The magnetostrictive actuator is capable of miniaturization and space saving as compared to heretofore, and can produce a greater amount of displacement.