Fine filter for purification of liquids having a cylindrical housing which is provided with an inlet for the liquid to be purified and an outlet for thickened dirty liquid and in the longitudinal centre of which a rotatable filter tube is arranged which essentially extends over the length of the cylindrical housing and the tube wall of which is provided with filter orifices and which is closed at one end and is connected at the other end to an outlet through which the purified liquid can be let off from the housing. The solution according to the invention directed towards improving the use characteristics with respect to conventional fine filters is characterised in that a shield tube is provided which surrounds the filter tube forming an intermediate space between the filter tube wall and the shield tube wall, the filter tube being closed at the end facing the outlet for the thickened dirty liquid and the intermediate space between the shield tube wall and the filter tube wall being open to the housing interior for the inlet of dirty liquid.
