A filter press comprising a pack of vertical filter plates with filter cloths (41, 42) positioned between each pair of filter plates, the pack of filter plates being positioned between two end plates (21, 22), at least one of the end plates (21, 22) being movable in order to close and open the pack of filter plates, a support structure extending horizontally in a longitudinal direction above the pack of filter plates, and at least one apparatus for washing the filter cloths (41, 42), said washing apparatus comprising: a carrier supported on the support structure, said carrier being movable along the support structure in the longitudinal direction, a support arm being composed of two link arms (310, 320), a first end of a first link arm being attached to the carrier with a first articulated joint, a second end of the first link arm being attached to a first end of the second link arm with a third articulated joint, a spray bar being attached to a second end of the second link arm with a second articulated joint, actuator means for turning the first link arm around the first articulated joint, first transmission means for turning the second link arm around the third articulated joint in synchronism with the turning of the first link arm, the first transmission means comprising a first cogwheel or cogged belt pulley supported rotatably on the carrier with an axis in the first articulated joint, a second cogwheel or cogged belt pulley supported rotatably on an axis in the third articulated joint, and a first chain or cogged belt forming a closed loop around the first cogwheel and the second cogwheel, second transmission means for turning the spray bar around the second articulated joint in synchronism with the turning of the second link arm, the second transmission means comprising a third cogwheel or cogged belt pulley supported rotatably on an axis in the third articulated joint, a fourth cogwheel or cogged belt pulley supported rotatably on an axis in the second articulated joint, and a second chain or cogged belt forming a closed loop around the third cogwheel and the fourth cogwheel, whereby the actuator means moves the spray bar in a plane between a spaced apart pair of filter plates downwards to a lower edge of the filter plates and upwards above an upper edge of the filter plates in order to wash the filter clothes (41, 42) between two spaced apart filter plates and the carrier moves the support arm and the spray bar in the longitudinal direction. a carrier supported on the support structure, said carrier being movable along the support structure in the longitudinal direction, a support arm being composed of two link arms (310, 320), a first end of a first link arm being attached to the carrier with a first articulated joint, a second end of the first link arm being attached to a first end of the second link arm with a third articulated joint, a spray bar being attached to a second end of the second link arm with a second articulated joint, actuator means for turning the first link arm around the first articulated joint, first transmission means for turning the second link arm around the third articulated joint in synchronism with the turning of the first link arm, the first transmission means comprising a first cogwheel or cogged belt pulley supported rotatably on the carrier with an axis in the first articulated joint, a second cogwheel or cogged belt pulley supported rotatably on an axis in the third articulated joint, and a first chain or cogged belt forming a closed loop around the first cogwheel and the second cogwheel, second transmission means for turning the spray bar around the second articulated joint in synchronism with the turning of the second link arm, the second transmission means comprising a third cogwheel or cogged belt pulley supported rotatably on an axis in the third articulated joint, a fourth cogwheel or cogged belt pulley supported rotatably on an axis in the second articulated joint, and a second chain or cogged belt forming a closed loop around the third cogwheel and the fourth cogwheel, whereby the actuator means moves the spray bar in a plane between a spaced apart pair of filter plates downwards to a lower edge of the filter plates and upwards above an upper edge of the filter plates in order to wash the filter clothes (41, 42) between two spaced apart filter plates and the carrier moves the support arm and the spray bar in the longitudinal direction.