The invention discloses a water purifier. The water purifier comprises a sealing box and a water storage tank, wherein the sealing box is fixedly connected to the top of the water storage tank, a connecting pipe is embedded in the top of the water storage tank, the top of the connecting pipe is fixedly connected with the bottom of a first water tank; a first water inlet pipe is fixedly connected to the top of the first water tank, a first water outlet pipe is embedded in the surface of the first water inlet pipe, and the first water outlet pipe is located at the right side of the first water inlet pipe; the first water outlet pipe communicates with the first water inlet pipe, the right end of the first water outlet pipe is fixedly connected to the left side of the sealing box, and a secondwater tank is fixedly connected to the top of the first water inlet pipe; and a second water inlet pipe is fixedly connected to the top of the second water tank. The problems that difficult operationof regular sewage discharging, disassembly washing and frequent replacement of filter elements are needed due to temporary storage of water cleaning filter dirt in a conventional non-self-cleaning water purifying device can be solved through arrangement of the sealing box, the first water outlet pipe and a second water outlet pipe.