A multifunctional filtering device for an aquarium mainly includes a filter box for being suspended at an aquarium. The filter box includes a pump motor for producing mixture of water and air and a vortex flow generator disposed at the center of the inner side of the bottom thereof and in communication with a water outlet disposed at the pump motor. A bubble collector is disposed at the top of the vortex flow generator. The filter box may be suspended inside or outside the aquarium. The filter box includes a water input pipe unit and a water output pipe unit which may be differently configured in accordance with the suspension position of the filter box. The water output pipe unit may be further disposed with a heating rod or ultraviolet sterilization lamp for heating or sterilizing breeding water in the aquarium.