An all-solid lithium secondary battery has excellent reliability including safety. However, in general, its energy density or output density is lower than that achieved by liquid electrolyte systems.The all-solid lithium battery includes a lithium ion-conducting solid electrolyte as an electrolyte. The lithium ion-conducting solid electrolyte is mainly composed of a sulfide, and the surface of a positive electrode active material is coated with a lithium ion-conducting oxide. The advantages of the present invention are particularly significant when the positive electrode active material exhibits a potential of 3 V or more during operation of the all-solid lithium battery, i.e., when redox reaction occurs at a potential of 3 V or more.