PURPOSE: To provide a device for automatically and continuously clean a long- sized sheet filter cloth discharged from a horizontal-plate filter.

CONSTITUTION: This horizontal-plate filter is provided with a cleaner consisting of a cleaning tank 10 provided adjacent the filter cloth 3 delivery side, guide rolls 11 and 12 horizontally furnished respectively on the upper end and lower end in the tank 10, a cleaning header 13 having plural spray nozzles opposed to the filter cloth 3 laid over the guide rolls 11 and 12 and a lifting means for reciprocating the header 13 along the filter cloth 3.