An acceleration sensor comprises first and second fixed electrodes formed on a substrate, a movable electrode disposed above and opposed to the first and second fixed electrodes and supported elastically on the substrate in a rocking manner by a first elastic support a mass member supported elastically on the substrate by a second elastic support and movable in relation to the substrate in response to the vertical acceleration, a joint portion jointing the movable electrode and the mass member at a predetermined distance from a rocking shaft of the movable electrode. The acceleration is measured on the basis of changes in a first capacitance which is created by the first fixed electrode and the movable electrode, and a second capacitance which is created by the second fixed electrode and the movable electrode. As a result, the acceleration sensor is excellent in impact resistance and high in reliability.
