Filtering device (100; 200) for high-viscosity fluids, with a housing (30; 230) and at least: - a screen carrier element (10, 20; 210, 220), which is dislaceably mounted in the housing (30; 230) and has in each case at least one screening space (12, 22; 212, 222), in which a filter element (11, 21; 211, 221) is arranged; - a feeding channel and a backflushing channel (31, 32) in the housing (30; 230), which channels can in each case be brought into connection with a soiled side of the screening space (12, 22; 212, 222); - a partial channel (34, 35; 35'; 234, 251, 254) in the housing, which, when viewed in the direction of flow during production, runs from the respective screening space (12, 22; 212, 222) to a discharge channel (33; 255), wherein the partial channel has at least one linear partial section (34, 35, 35'; 254), from which the discharge channel (33; 255) branches off laterally; - a displacing piston (40; 40'; 40"; 240), which can be inserted into the partial channel (34, 35; 35'; 254) and through which the fluid located in the partial channel (34, 35; 35'; 254) can be forced counter to the direction of flow during production through the filter element (11, 21; 211, 212) into a backflushing channel (31, 32) in the housing, characterized - in that the displacing piston (40; 40'; 40"; 240) has at least an inner fluid line (42; 42'; 42"; 242), which extends from an inlet opening (41; 41'; 41") at the displacing piston (40; 40'; 40"; 240) to an outlet opening (43; 43'; 43"; 243) at its circumference; - in that the outside diameter of the displacing piston (40; 40'; 40"; 240) corresponds, at least in some regions thereof, to the inside diameter of the partial channel (34, 35; 35'; 254); in that, in a production position, the displacing piston (40; 40'; 40"; 240) can be positioned with its outlet opening (43; 43'; 43"; 243) in front of the mouth of the discharge channel (33; 255) in the partial channel (34, 35; 35'; 254); - in that the displacing piston (40; 40'; 40"; 240) is retractable into a backflushing starting position for storing fluid within the partial channel (34; 2), wherein, along a backflushing displacement path of the displacing piston (40; 40'; 40"; 240), the mouth of the discharge channel into the partial channel (35; 35') is covered by the outer wall of the displacing piston (40; 40'; 40"; 240) and/or the outlet opening (43; 43'; 43") of the displacing piston (40; 40'; 40"; 240) is covered by the inner wall of the partial channel (34, 35; 35'). - a screen carrier element (10, 20; 210, 220), which is dislaceably mounted in the housing (30; 230) and has in each case at least one screening space (12, 22; 212, 222), in which a filter element (11, 21; 211, 221) is arranged; - a feeding channel and a backflushing channel (31, 32) in the housing (30; 230), which channels can in each case be brought into connection with a soiled side of the screening space (12, 22; 212, 222); - a partial channel (34, 35; 35'; 234, 251, 254) in the housing, which, when viewed in the direction of flow during production, runs from the respective screening space (12, 22; 212, 222) to a discharge channel (33; 255), wherein the partial channel has at least one linear partial section (34, 35, 35'; 254), from which the discharge channel (33; 255) branches off laterally; - a displacing piston (40; 40'; 40"; 240), which can be inserted into the partial channel (34, 35; 35'; 254) and through which the fluid located in the partial channel (34, 35; 35'; 254) can be forced counter to the direction of flow during production through the filter element (11, 21; 211, 212) into a backflushing channel (31, 32) in the housing, - in that the displacing piston (40; 40'; 40"; 240) has at least an inner fluid line (42; 42'; 42"; 242), which extends from an inlet opening (41; 41'; 41") at the displacing piston (40; 40'; 40"; 240) to an outlet opening (43; 43'; 43"; 243) at its circumference; - in that the outside diameter of the displacing piston (40; 40'; 40"; 240) corresponds, at least in some regions thereof, to the inside diameter of the partial channel (34, 35; 35'; 254); in that, in a production position, the displacing piston (40; 40'; 40"; 240) can be positioned with its outlet opening (43; 43'; 43"; 243) in front of the mouth of the discharge channel (33; 255) in the partial channel (34, 35; 35'; 254); - in that the displacing piston (40; 40'; 40"; 240) is retractable into a backflushing starting position for storing fluid within the partial channel (34; 2), wherein, along a backflushing displacement path of the displacing piston (40; 40'; 40"; 240), the mouth of the discharge channel into the partial channel (35; 35') is covered by the outer wall of the displacing piston (40; 40'; 40"; 240) and/or the outlet opening (43; 43'; 43") of the displacing piston (40; 40'; 40"; 240) is covered by the inner wall of the partial channel (34, 35; 35').