To provide an acceleration sensor and a sensor network system having a construction in which the consumption of power to be consumed can be reduced and the sensor itself can be miniaturized without using any piezoelectric sensor or piezoelectric bimorph.An acceleration sensor device provided with an acceleration sensor which is an electrostatic induction conversion device for conversion between electric energy and kinetic energy, which comprises a conductor and an electret moving relatively to the conductor, said acceleration sensor device having: an acceleration detection unit to detect a signal corresponding to acceleration, from an AC voltage output by the acceleration sensor; a rectification unit to rectify the AC voltage; and a power supply circuit having a battery to power circuits in the device to work, to charge the battery with the rectified voltage as electric energy.