A filter having a back-flushing cleaning device, comprising a 3/2-way valve (F1), a second valve (F2), and a third valve (F3). The 3/2-way valve (F1) is provided with a P1 port, an A1 port, and a B1 port. The second valve (F2) is provided with a P2 port and an A2 port. The third valve (F3) is provided with a P3 port and an A3 port. The P1 port is connected to a water inlet (3), the A2 port is connected to a water outlet (4), and the A3 port is connected to a drain outlet (5). The A1 port and P3 port are connected to a water incoming region of a filtering element (2), and the B1 port and P2 port are connected to a water outgoing region of the filtering element (2). When P1 is open to A1, P2 is open to A2, and P3 is close to A3, the filter is in a filtering operating position; when P1 is open to B1, P2 is close to A2, and P3 is open to A3, the filter is in a back-flushing cleaning operating position. In this way, the present invention enables switching between the filtering operating position and the back-flushing operating position by switching three valve gates at the same time without changing water flow directions of the water inlet and water outlet. The present invention provides a simple overall process, convenient operation, a compact pipeline structure, and a neat design of a filter cartridge.