The utility model provides a water purifier which comprises a water inflow control device and a first filtering device which are sequentially arranged on the waterway of the water purifier; the outlet of the first filtering device is connected with a first water-dividing path and a second water-dividing path; the first water-dividing path is connected to a purified water storage part and/or a purified water output part through a valve; the second water-dividing path is connected to a wastewater treatment part; a non-return valve is arranged between the first filtering device and the valve, and a first pressure switch is arranged at the downstream of the non-return valve; the second pressure switch is arranged between the non-return valve and the valve; and a controller is electrically connected with the water inflow control device, the first pressure switch and the second pressure switch respectively. The water purifier provided by the utility model effectively solves the problem of resource waste caused by frequent starting of a conventional water purifier of which the pressure switch has an over narrow pressure area.