The utility model provides a purified water producing device. A raw water tank, a raw water pump, a double-layered filter material filter, an active carbon filter, an antisludging agent injecting system, a reverse osmosis device and a product water tank are connected together in series through pipelines and valves; a back-flush water tank is connected in parallel below the raw water tank; the back-flush water tank, a back-flush pump, a cleaning water tank, a cleaning water pump, a cleaning security filter and a security filter are connected together in series through the pipelines and the valves; the cleaning security filter, the cleaning water pump, the cleaning water tank and the reverse osmosis device are connected in parallel; and the reverse osmosis device is connected in series with the security filter. The purified water producing device has the advantages of effectively removing pollutants such as scale and the like produced in equipment, greatly guaranteeing product quality and prolonging the service life of the equipment.