Abstract: Provided is a rotor structure of a radial type synchronous motor having a rotor core (10) is held between permanent magnets (12) wherein end plates (14) are attached to ends of the rotor (8) in a direction of the central axis (6) of the rotor, each of which plates is provided with projecting portions (16) to regulate a radial position of an outer face of the rotor core. This prevents a projection of the rotor core and permanent magnets in the radial direction due to a centrifugal force caused by a rotation of the rotor. Therefore, a rotor structure able to withstand a strong centrifugal force can be provided.