A solid state battery includes: a negative electrode layer including a negative electrode active material; a positive electrode layer including a positive electrode active material; and a solid electrolyte layer installed between the negative electrode layer and the positive electrode layer, wherein the solid electrolyte layer contacts the negative electrode layer and the positive electrode layer, and wherein the solid state battery satisfies Equation 1: {(Vp−V980)/Vp×100}≦3%  Equation 1 wherein Vp is a total volume of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer, and V980 is a total volume of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer under the total pressure of about 980 megapascals.