A backwash filter, in particular for highly viscous media, comprising a filter body (2) provided in a casing (1) and forming a cylinder jacket, wherein the casing (1) and the filter body (2) are rotatable about the axis of the filter body (2) relative to one another and wherein the filter body (2) separates a medium inflow space (14) from a medium outflow space (16), and comprising a flushing agent discharge channel (10) extending along a generatrix of the filter body (2), which flushing agent discharge channel (10) is movable relative to the filter body (2) and can be brought into flow connection with the filter body (2) across the entire length thereof and across the entire circumference thereof, with the formation of a stream of flushing agent flowing into the flushing agent discharge channel (10), is characterized, for increasing the efficiency of backwashing and of the throughput as well as for protection of the filter material, in that the flow connection always occurs only across a portion of the longitudinal extension (20) of a generatrix of the filter body (2).