Activated carbon fiber cloths (AC) and hydrophobic microporous polypropylene (PP) membrane, both modified by acetone aldol condensation products, and filled with polymer hydrogel were used as electrodes, separator and electrolyte in electric double layer capacitors (EDLCs). Polymer hydrogel used was based on poly(acrylamide) (PAAM), KOH and water. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry and galvanostatic charge–discharge cycle tests and also by impedance spectroscopy, compared with a case of the capacitor with only a KOH aqueous solution used as an electrolyte. As a result, the capacitor with polymer hydrogel was found to exhibit higher capacitance than that with the KOH aqueous solution and an excellent high-rate dischargeability. The above results provide valuable information to explore novel composition of EDLCs.