The invention discloses a settling tank which comprises a settling tank body; the top of the settling tank body is open and the other sides of the settling tank body are closed; the front tank wall ofthe settling tank body is provided with a liquid inlet; two lower vertical baffle plates are arranged in the settling tank body; the upper edge of each lower vertical baffle plate is lower than thatof the settling tank body; the interior of the settling tank body is divided into a first settling tank, a second settling tank and a clear water tank by the two lower vertical baffle plates; an uppervertical baffle plate is arranged in each settling tank; the upper edge of each upper vertical baffle plate is flush with that of the settling tank body; and the lower edge of each upper vertical baffle plate is higher than the tank wall at the bottom of the settling tank body and is lower than the upper edge of each lower vertical baffle plate. The settling tank has the advantages that substances easy to settle are separated out from washing water effectively in time, the settling separating effect is good, the energy consumption is not generated in the separating process, the environment isnot polluted, waste of water energy is avoided, and the settling tank is simple in structure, convenient to mount, easy to clean, and low in operation and use costs.