Provided herein is an artificial muscle capable of being miniaturized, realizing precision movement, and performing selective relaxation/contraction deformation according to the power output necessary in the muscle, the muscle including a first operation unit that includes electro-active polymer where relaxation-deformation occurs based on electric energy being applied; a heating unit that generates heat energy based on the electric being applied; a second operation unit that has a yarn structure and where contraction-deformation occurs based on the heat energy generated in the heating unit; and a control unit that applies electric energy to the first operation unit and the heating unit.