Provided is a microphase-separated structure membrane including a block copolymer in which a hydrophilic polymer component and a hydrophobic polymer component are coupled to each other via a structural unit having a reactive group, an electron acceptor or electron donor, or a dye. In the microphase-separated structure membrane, a cylinder structure composed of the hydrophilic polymer component lies in a matrix composed of the hydrophobic polymer component and is oriented in the direction perpendicular to the membrane surface, and the structural unit having a reactive group, an electron acceptor or electron donor, or a dye lies between the matrix and the cylinder structure.