Disclosed is a device for varying capacitance which pertains to the field of application of electronic devices and components. The technical essentials of the present invention lie in that: two dielectrics are disposed in parallel with an isolation layer interposed therebetween; the two dielectrics each are connected to an electrode at the same one end face thereof; the other end face of each of the two dielectrics is provided with an elastic conductive pad; a gasket is provided between the two dielectrics and the elastic conductive pads. The relative position and compressed area between the elastic conductive pads and the dielectrics vary according to the magnitude of the external force so that the capacitance between the electrodes of the dielectrics is varied accordingly within a certain range. Therefore, once the value and the variation of the capacitance between the electrodes are measured, the magnitude and the status of the external force which brings about the variation of the capacitance can be obtained. The device of the present invention has a simple structure and high sensitivity. Also, it has a definite zero initial value and a maximum value of the capacitance, and therefore is easy for handing and measurement.