Provided is an electrically conductive elastomer with high stretchability and high durability. A method of synthesizing an electrically conductive elastomer includes (a) preparing a eutectic solvent by mixing quaternary ammonium salt and organic acid, and (b) adding and blending the eutectic solvent with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), a photocuring agent, and a crosslinker and performing photopolymerization.