Abstract: A bean sifting device which comprises a water-supply assembly, a water tank, a floating-sifting tank, and a supporting frame; the water-supply assembly can have water in the water tank to be forced by use of a pump in the water-supply assembly to flow into the floating-sifting tank through a pipe and slanting water outlet; the water would generate a whirl by use of a round and curved bottom and the wall of the floating-sifting tank; as a result of the effect of a centrifugal force and the different specific gravity gravity of beans, the bad beans will float in the upper water in the tank, and will flow into the water damping area to pass through a slot hole, a round passage and an exhausting port; finally, the bad beans will flow in a sieve basket so as to fulfill a purpose of sifting beans in different classes automatically.