Disclosed are: a polymer electrolyte membrane which can prevent ionic conductor loss even upon the occurrence of chemical degradation in the ionic conductor according to long term use and thus can be significantly improved in chemical durability; a manufacturing method therefor; and an electrochemical device comprising same. The polymer electrolyte membrane of the present disclosure comprises a polymer electrolyte material. The polymer electrolyte material comprises an ionic conductor and a crosslinker unbound to the ionic conductor. The crosslinker has at least one cross-linkable functional group which can couple with the ionic conductor that has been degraded, thereby causing crosslinking with the ionic conductor.