The invention discloses an automatic water supplementing device for cattle raising. The device comprises a sink, a horizontally-arranged supporting plate is welded to the side wall of one side of thesink, a water storage box is connected to the top end of the supporting plate, a water outlet pipe is connected to the bottom end of the water storage box, an electromagnetic valve is connected to thewater outlet pipe, the end, away from the water storage box, of the water outlet pipe is communicated with the interior of the sink, a circulating pipe is arranged at the side wall of one side of thesink, the two ends of the circulating pipe are communicated with the interior of the sink, a conveying pump and a treating box are connected to the circulating pipe, the side walls of the top end andthe bottom end of the treating box are provided with symmetrically-arranged clamping grooves, a first filter net and an adsorption box are clamped between the clamping grooves located at the same vertical face, and a control box is connected to the side wall of one side of the water storage box. Due to cooperation of a liquid level sensor and a water storage box, the water source inside the sinkcan be automatically detected, when the water source is excessively low, automatic water supplementing is performed, artificial repeated addition is not needed, and practicability is improved.