PURPOSE: To improve the dehydration effect of sludge and the like considerably by revolving a large diameter rotary cylindrical frame body mounted with a multiplicity of small diameter rolls in pressure contact with endless filter cloth belts at prescribed intervals in the circumferential direction at the speed differing from that of the endless filter cloth belts.

CONSTITUTION: A multiplicity of small diameter rollers 15 performing dehydration cooperatively with the superposed parts of two steps of upper and lower endless filter cloth belts 2, 3 are disposed to a large diameter rotary cylindrical flame body 17 by leaving intervals in its circumferential direction. Disc-like end plates 19 are mounted to both end parts of a revolving shaft 18 of the body 17, and the shafts 16 of the respective rollers 15 are mounted freely rotatably to the circumferential edge parts of the end plates 19, whereby a press roller device 5 is formed. The shaft 18 revolves at the speed differing from the traveling speed of the belts 2, 3. Since the superposed parts of the belts 2, 3 are put on the device 5 at a large wrapping angle by means of the end roller of a primary press roller group 4 and a direction change roller 9, they receive press shearing dehydration treatment and this improves dehydration efficiency.