PURPOSE: To provide a filter capable of substantially preventing gas exchange between a place for cleaning of filter plates and a circumstance, especially the place, wherein the filer press which hold filter plates alredy cleaned is placed.

CONSTITUTION: This filter has at least one filter press 1 equipped with plural filter plates 8 and at least one cleaning plant 12 washing the filter plates, a cleaning plant 12 is placed apart from filter press 1 in order to prevent air exchange between the plant and the filter press 1, and a transport device 30 for transporting the filter plates is arranged between filter press 1 and the cleaning plant 12.