An electromechanical device includes a central shaft; a rotor having a rotor magnet disposed along the periphery of the central shaft; a stator disposed on the periphery of the rotor; and a rotation mechanism connected to the rotor and used for transfer of a rotational driving force, wherein in the rotor, between the central shaft and the rotor magnet, a space which opens in at least one of an axial direction of the central shaft and houses at least part of the rotation mechanism is formed.