Filtration device for filtering liquids, - having a housing which has a dirty-side inlet connection and a clean-side outlet connection, - having a cylindrical filter body through which the liquid can flow radially and which is rotatably arranged in the housing about the longitudinal centre axis thereof and which in the housing radially separates an outer dirty side from an inner clean side, - having a rotary drive which is for rotatably driving the filter body and which has a hollow drive shaft which extends through a stationary sleeve which is arranged in the housing at the clean side and which is coupled to the filter body for torque transmission, - having a backwash device for backwashing a peripheral segment of the filter body, which has a discharge channel which is arranged in a stationary manner at the dirty side in the housing and which has at the inlet side at least one inlet opening which faces the peripheral portion to be cleaned and which is connected at the outlet side to a discharge channel connection which is formed on the housing, - wherein the backwash device has a supply channel which is arranged in a stationary manner at the clean side in the housing and which has at the outlet side at least one outlet opening which faces the peripheral portion to be cleaned and which is connected in fluid terms to the inner space of the drive shaft, characterised in - that the drive shaft has in the region of the sleeve at least one radial opening, - that the sleeve has at least one radial opening, - that there is provided a clean-side fluid path which leads from the clean side through the sleeve and through the drive shaft into an inner space of the drive shaft and from there into the supply channel. - having a housing which has a dirty-side inlet connection and a clean-side outlet connection, - having a cylindrical filter body through which the liquid can flow radially and which is rotatably arranged in the housing about the longitudinal centre axis thereof and which in the housing radially separates an outer dirty side from an inner clean side, - having a rotary drive which is for rotatably driving the filter body and which has a hollow drive shaft which extends through a stationary sleeve which is arranged in the housing at the clean side and which is coupled to the filter body for torque transmission, - having a backwash device for backwashing a peripheral segment of the filter body, which has a discharge channel which is arranged in a stationary manner at the dirty side in the housing and which has at the inlet side at least one inlet opening which faces the peripheral portion to be cleaned and which is connected at the outlet side to a discharge channel connection which is formed on the housing, - wherein the backwash device has a supply channel which is arranged in a stationary manner at the clean side in the housing and which has at the outlet side at least one outlet opening which faces the peripheral portion to be cleaned and which is connected in fluid terms to the inner space of the drive shaft, characterised in - that the drive shaft has in the region of the sleeve at least one radial opening, - that the sleeve has at least one radial opening, - that there is provided a clean-side fluid path which leads from the clean side through the sleeve and through the drive shaft into an inner space of the drive shaft and from there into the supply channel.