A molded solid electrolyte comprising a polymer composition comprising 50 to 100 wt.% 1,2-polybutadiene having a 1,2-vinyl bond content of 70 % or higher and a crystallinity of 5 to 50 % and 0 to 50 wt.% polar rubber. The molded electrolyte combines high ionic conductivity with high processability, while the molded electrode has high electrode activity. By using the electrolyte and the electrode, an electrochemical element having excellent operating characteristics can be obtained.