An actuator is provided and has an electro-mechanical conversion element; a driving frictional member attached at one end of the electro-mechanical conversion element with respect to a direction of expansion and contraction thereof; a plurality of driven members frictionally engaged with the driving frictional member; a plurality of biasing units, each biasing one of the plurality of driven members to be frictionally engaged with the driving frictional member; and a biasing-force adjusting unit that adjusts respective biasing-forces of the plurality of biasing units.