A substrate forming a sensor element is connected to a non-inverting input terminal of an operational amplifier, and a common voltage is applied thereto from a reference voltage supply circuit to fix them to the same potential. Thus, the impedances of the non-inverting input terminal and of the inverting input terminal of the operational amplifier are matched with respect to the power source. Therefore, noise superposed on a power source line can be greatly decreased by noise-removing characteristics determined by CMRR characteristics of the operational amplifier. As a result, a capacitive-type acceleration sensor exhibits sensor characteristics of frequency noise suppressing effect.