An aquarium overflow device capable of preventing adverse effects by suction noise of an overflow pipe. The aquarium overflow device according to the present invention is equipped with a water storing portion 52 for storing water W in an aquarium, an overflow pipe 54 extended upwardly in the water storing portion 52 and having an upper end opening for introducing the water W stored in the water storing portion 52 and a lower end opening for discharging the water which is open to a bottom wall side of the water storing portion 52, and a sound preventing cover 47 provided in the water storing portion 52 so as to cover the entire region of the above-water portion of the overflow pipe 54.