To provide a support structure of circular filtration plates in a screw-type filtration/dehydration apparatus, through which the water to be filtered is made to fall down easily to cause each of the plates to exhibit an excellent filtration/dehydration function, which is convenient suitably when the space between the adjacent plates is washed after the filtration/dehydration work is completed and facilitates the work of exchanging the worn plates and whose maintenance is made excellent.

A screw conveyer 11 is engaged in a central hole 10 of a cylindrical filter medium 11 obtained by stacking many circular filtration plates 2 and circular movable plates 3 alternately at narrow intervals. Several supporting rods 7 are disposed along the outer periphery of the medium 11 so that the rods 7 are kept in the non-contact states with each of the plates 3. Engaging parts 5 arranged at several positions of the outer circumferential edge of each of the plates 3 are engaged with the rods 7 respectively so that the medium 1 can be kept in the cylinder-formed state.