PURPOSE: To simplify the structure of a filter and to reduce the cost thereof by providing a horizontal type filter tank and performing the stirring of cake and the function for discharging cake by means of only the rotary mechanism of a center shaft.

CONSTITUTION: Slurry to be fed is introduced through an inlet 8 for liquid of a horizontal type closed tank 7 and filtered by a filter medium 10 provided on a filter plate 9. Filtrate is discharged through an outlet 11 for filtrate via the underside of the filter plate 9 and cake 12 is deposited on the filter medium 10. After if necessary, introducing washing liquid through an inlet 13 thereof, a normally and reversely rotatable rotary shaft 15 provided to the central position of the tank 7 is rotated by a driving gear 6'.The filtered cake 12 is peeled from the surface of the filter medium 10 by means of stirring blade 18 groups having multiple blades 14, 14' which are fitted to the rotary shaft 15 at definite angle to the axial direction via supporting arms 17, 17' from central sleeves 16 externally fitted to the rotary shaft 15 and cake 12 is stirred and washed.