A lens driver includes a lens unit, a polymer actuator, and an orthogonal transformation mechanism. The lens unit includes a lens holding frame having a pressed portion at an outer peripheral surface of the lens unit, a lens being held thereby. The lens unit is movable in an optical-axis direction of the lens. The polymer actuator is arranged outside the outer peripheral surface and having an electrode to which a voltage is applied. The polymer actuator is bent in a direction orthogonal to the optical-axis direction and presses the pressed portion in that direction when the voltage is applied to the electrode. The orthogonal transformation mechanism converts a force in a pressing direction into a moving force in the optical-axis direction and moves the lens unit in the optical-axis direction when the pressed portion of the lens holding frame is pressed by the bent polymer actuator.