Disclosed herein is an improvement in a filter of the type having a plurality of filtering plates vertically spaced at fixed intervals to interpose filtering spaces therebetween and as many scrapers laid outwardly from the axis of the stack of filtering plates and inserted one each into the filtering spaces, i.e. between the adjacent filtering plates, the improvement which includes giving each filtering plate a perfectly circular periphery so as to avoid formation of any protuberance from the circumferences and, at the same time, disposing the scrapers so as to keep sliding contact with the adjacent filtering plates.