The utility model relates to a waste water treating and reusing device, comprising a sandbasin, a coagulation sedimentation tank, a reverse osmosis membrane processing device and a clear water tank which are communicated with the sandbasin in turn and provided with chemical feed boxes. The lower part of the reverse osmosis membrane processing device is communicated with the lower part of the clear water tank through the water outlet pipe of the film. A backwashing water inlet pipe which is communicated with the upper part of the reverse osmosis membrane processing device is arranged on the upper part of the clear water tank. A backwash water back flow pipe is arranged on the low part of the reverse osmosis membrane. The utility model is chiefly applied to treat and reuse for the waste water for washing cars, cleaning ships and bathing. The waster water after preprocessed can reach the standard of drinking water, and the salinity, organic matter, scouring agent, suspended matter, etc. in the waste water are exhausted together with the sludge. The removal efficiency of pollutants of the entire waste water treating and reusing device is increased 80%, the water conservation is reached 70%, and the water charge is saved 50%. The waste water treating and reusing device overcomes the disadvantages of poor wastewater effluent water quality in the previous waste water treating devices, increased salt quantity after cycling, poor stability, etc.