A phase-separated polymer electrolyte membrane is provided which has a low degree of swelling in water and methanol, excels in resistance to water and methanol, and has high methanol barrier property and a low membrane resistance. An electrode-phase-separated polymer electrolyte membrane joint using the membrane, a method for manufacturing the membrane and joint, and a fuel cell using them are also provided. There is provided a polymer electrolyte membrane having two phases: a domain phase comprising an electrolyte polymer (a) and a matrix phase comprising a polymer (b) that inhibits swelling of component (a), the membrane also having a three-dimensional structure that can conduct protons and substantially connects the domains of (a).