The invention provides a filtering device and a method of manufacturing same. The filtering device (1) which includes a depth filter (10) and a housing (9) for containing the depth filter and which has a primary filtering unit (4) for filtering raw water (RW). The housing (9) is provided with a raw water supply opening (18) for supplying the raw water (RW) to the depth filter (10), a filtered-water take-out opening (16), a fluid supply opening (24) for supplying reverse washing fluid to the depth filter (10), and a discharge opening (22) for discharging fluid (A) having reversely washed the depth filter (10) and also discharging the raw water (RW). The diameter of pores in a filtering film which forms the depth filter (10) is in the range from 1 to 25 [mu]m. The filtering device is also provided with a communication path (15) for connection between a filtered-water path (8) connected to the filtered-water take-out opening (16) and a discharge path (14) connected to the discharge opening (22), and with a fifth automatic on-off valve (MV5) for opening and closing the communication path (15).