A method for manufacturing a liquid flow passage unit that is disposed between a liquid supply source storing liquid and a head main body and that forms a part of a flow passage leading from the liquid supply source to the head main body, includes bringing a film member into contact with a protrusion formed on the edge of an opening of a flow passage for liquid formed in a main body member made of resin, so as to cover the opening with the film member, pressing the film member covering the opening toward the flow passage, so as to apply a predetermined tension to the film member, and integrally molding a sealing member by pouring resin on the edge of the tensioned film member, so as to fix the film member between the sealing member and the main body member.