A rain water filter is disclosed. The rain water filter includes a horizontal inlet and a horizontally arranged residual water outlet which are slightly offset in relation to each other. A pipe with a longitudinal slot connects to the inlet and the pipe leads into the residual water outlet. An adhesive filter which is in the form of a tunnel-shaped half-shell is arranged below the longitudinal slot, where the lateral walls are the filter surfaces of the filter. Due to the adhesion effect, the water which flows past is suctioned inwards where it passes through the longitudinal opening into a tank and from there, for example, into a cistern via a filter water outlet. The water running off from the side walls is collected on the base of the hollow cylinder and from there is guided to the residual water outlet.