Swelling/contracting filter

A swelling/contracting filter comprises a bag-like filtrating cloth allowed to swell and contract and a flow passage material disposed in the filtrating cloth for collecting and discharging a liquid filtrated by the filtrating cloth, and the filter is characterized in that the filtrating cloth and the flow passage material are both formed of flexible materials. Accordingly, the filter itself can be freely bent and folded. As a result, even if the filter is long or densely disposed in a vessel, the filter can be easily handles and removed by bending and folding, and the replacement and maintenance of the filtrating cloth and the filter can be extremely easily performed.