A reverse osmosis membrane filtering device, comprising: a container having an inlet for unprocessed water, an outlet for concentrate water, and at least one permeate-water outlet; a water-collecting member including a plurality of water collecting pipes, and having a plurality of sections each of which extends inside the container and has a plurality of water collecting apertures; a plurality of filter assemblies disposed around the plurality of sections, one filter assembly for each section, each filter assembly including a filter member comprising a reverse osmosis membrane, an axial direction channel extending along the plurality of water collecting pipes, and a water collecting channel extending toward the plurality of water collecting apertures; at least one seal member disposed inside the water-collecting member; at least one insertion tube (32a,32b) inserted inside at least one water collecting pipe of the plurality of water collecting pipes and defining two permeate-water channels including a first permeate-water channel (62a,62d) between the at least one water collecting pipe and the at least one insertion tube and a second permeate-water channel (62b,62c) inside the at least one water-insertion tube (32a,32b), with the at least one seal member constituting a connector which is inserted into end portions of two adjacent water collection pipes and is sealing a gap between the at least one water collecting pipe and the at least one insertion tube (32a,32b), so that the first and second permeate-water channels (62a,62d;62b,62c) correspond to two of the sections of the water-collecting member; and a pressure adjusting device configured to increase a pressure of one of the two permeate-water channels to a pressure higher than that of the other one of the permeate-water channels. a container having an inlet for unprocessed water, an outlet for concentrate water, and at least one permeate-water outlet; a water-collecting member including a plurality of water collecting pipes, and having a plurality of sections each of which extends inside the container and has a plurality of water collecting apertures; a plurality of filter assemblies disposed around the plurality of sections, one filter assembly for each section, each filter assembly including a filter member comprising a reverse osmosis membrane, an axial direction channel extending along the plurality of water collecting pipes, and a water collecting channel extending toward the plurality of water collecting apertures; at least one seal member disposed inside the water-collecting member; at least one insertion tube (32a,32b) inserted inside at least one water collecting pipe of the plurality of water collecting pipes and defining two permeate-water channels including a first permeate-water channel (62a,62d) between the at least one water collecting pipe and the at least one insertion tube and a second permeate-water channel (62b,62c) inside the at least one water-insertion tube (32a,32b), with the at least one seal member constituting a connector which is inserted into end portions of two adjacent water collection pipes and is sealing a gap between the at least one water collecting pipe and the at least one insertion tube (32a,32b), so that the first and second permeate-water channels (62a,62d;62b,62c) correspond to two of the sections of the water-collecting member; and a pressure adjusting device configured to increase a pressure of one of the two permeate-water channels to a pressure higher than that of the other one of the permeate-water channels.