A force sensor comprises a substrate having a movable unit which is displaceable in response to one of an applied force and acceleration; an electron emission unit having a cathode for emitting electrons in accordance with an applied potential; an electron absorption unit having an anode for capturing electrons emitted from the cathode, the electron emission unit and the electron absorption unit being formed on a surface of the substrate; and a control unit for, on the basis of the displacement of the movable unit, controlling the electron capturing efficiency of the anode with respect to electrons emitted from the cathode.