ENCODER

An encoder includes: a disk having a pattern of slits arranged in one direction; a light emitting element for emitting light toward the pattern of the disk; a plurality of light receiving elements arranged in the direction in which the slits are arranged and configured to receive the light emitted from the light emitting element, by way of the slits; and an optical element configured to magnify an image formed by the light which is emitted by the light emitting element and then reaches the optical element by way of the slits and to transmit the magnified image toward the light receiving elements, the optical element having a magnification ratio that is set so as to magnify the formed image at least in the direction in which the light receiving elements are arranged, depending on the pitch of the slits and the pitch of the light receiving elements.