Abstract: The polymer electrolyte membrane (PEM) of the present invention charged with a proton conductor in the collimated pores of a polymer film that is equipped with a plurality of such collimated pores in the direction of the film thickness is characterized with a relative standard deviation (LVar/LAve) equal to or below 0.3 wherein LAve and LVar represent an average value of L, distances between centers of the adjacent collimated pores and the standard deviation thereof, respectively. In addition, the PEM of the present invention can be prepared by installing a plurality of pores in the polymer film in the direction of the film thickness using photolithography and, subsequently, charging the above collimated pores with a proton conductor. Such constitution of the present invention can provide PEM with a small size, and improved performance and productivity; and also improvement of cell performance by inhibiting methanol permeation of DMFC that uses methanol as its fuel.