The actuator disclosed herein comprises a coil, a magnet and a magnetism detection element. The magnet is configured to move a predetermined distance relative to the coil via a magnetic force generated when current is passed through the coil. The magnet includes a first polarization line perpendicular to the direction in which the magnet moves relative to the coil, and a second polarization line parallel to the first polarization line. The magnetism detection element is configured to detect the position of the magnet. The coil faces the first polarization line and the magnetism detection element faces the second polarization line. The length from the second polarization line to a first end of the magnet is equal to or more than 1.25 times the predetermined distance. The first end of the magnet is closer to the magnetism detection element than to the coil.