A polymer electrolyte according to the invention is represented by the following formula (1). In the formula (1), R1 and R2 are each independently hydrogen or CH3, R3 is any of C2H4, CH(CH3)CH2, and (CH2)3, m and n are each a copolymerization ratio of a structural unit in parentheses, and when m and n are set as follows: m+n=10, m and n satisfy the following formulae: 1≤m≤5 and 5≤n≤9, and p is 2 or more and 8 or less.