A filter device for filtering liquids including a filter membrane, a main body which is arranged upstream from the filter membrane, and which has a feed channel perpendicular to the surface of the filter membrane, a gap extending between the filter membrane and the main body forming a tangentially directed cross-flow, and a return channel which is used to return the tangential flow to the feed channel. The flow is primarily returned thereto by means of a contraction in the feed channel at the mouth of the return channel. Preferably, a solid separator is disposed in the return channel. At least one baffle element is arranged in the feed channel in order to create a turbulent flow. The tangential flow along the filter membrane is used to clean said membrane.