An automatic water supply control device is disclosed. A power processing unit processes an alternating current outputted by a micro hydro generator and provides a stable direct current. The automatic water supply control device uses a capacitor and a capacitor matrix for storing electric energy. A sensing unit detects changes from an environment such as human proximity, temperature and humidity and outputs sensing signals. A micro controller set receives the sensing signals sent by the sensing unit in order to control an electromagnetic drive unit and drive the electromagnetic coil. The micro controller set also controls an electromagnetic drive unit to drive an electromagnetic coil for supplying water and performing charging based on a logical setting, when an output voltage value of a step-down voltage conversion circuit is lower than a preset voltage value.