An electric double layer capacitor is proposed which is constructed by sandwiching a laminated body of a pair of polarizable electrodes consisting of a porous solid conductive material each impregnated with an electrolytic solution and a platelike ion permeating separator member, between a pair of collectors for external connection terminals, and housing the aggregate in a gasket, wherein the gap between the inner surface of the gasket and the outer surface of the laminated body is filled with an auxiliary electrolytic solution. The auxiliary electrolytic solution consists of glass fibers or water absorbing polymer impregnated with gelatinous electrolytic solution or a liquid electrolytic solution, and replenishes the lost portion due to evaporation and leakage of the electrolytic solution of the electric double layer capacitor. Moreover, this auxiliary electrolytic solution acts as a buffer to mechanical impact externally applied to the capacitor. Therefore, the electric double layer capacitor according to this invention has excellent resistance to high temperature and resistance to impact.