To provide an attitude control device and an attitude control method of opening/closing filter plates in a filter press for keeping a movement attitude of the filter plates, by controlling a plurality of independent hydraulic cylinders, by measuring parallelism and perpendicularity when moving the filter plates.

A filter press 1 freely opens/closes a large number of filter plates 5 ..., by connecting tips of rods 10 of one sides of a plurality of parallel hydraulic cylinders 9 ... whose another sides are disposed to a rear frame 3, to a movable head 11 arranged at an end of parallel filter plates. In the filter press 1, a vertical or lateral displacement difference L of the filter plates 5 is detected by a detector 13 when opening/closing the filter plates 5, a detected signal is transmitted to a control device 14 to be compared with a predetermined reference value L0, and in a case that the displacement difference L is larger than the reference value L0, an opening of a flow control valve 17 is adjusted so that rod lengths of the parallel hydraulic cylinders 9 are controlled to be synchronized. Thus, the displacement difference L when transferring the filter plates 5 is kept in a stable state.