An elastic wave control element is inserted into a propagation path for an elastic wave or installed in an oscillator to allow the elastic wave in a selected frequency to be damped, reflected, or transmitted. A piezoelectric material 1 is provided with a pair of electrodes between which a negative capacitance circuit A is connected to allow a loss factor of the negative capacitance circuit A in a selected frequency or frequency band to be matched with a dielectric loss factor of the piezoelectric material 1.