A solid-state lithium battery in which a thermal stability is improved. The solid-state lithium battery comprises a cathode active material layer containing a cathode active material, an anode active material layer containing an anode active material, and a solid electrolyte layer formed between the cathode active material layer and the anode active material layer. The cathode active material is an oxide active material, at least one of the cathode active material layer and the solid electrolyte layer contains a sulfide solid electrolyte material, the sulfide solid electrolyte material comprises a Li element, a P element, a S element, and an I element, and the cathode active material layer contains a specific phosphate ester.