The present invention provides a method of efficiently producing a lithium ion conductive inorganic solid electrolyte having high ionic conductivity, including: conducting a melt reaction of lithium sulfide containing 0.15 mass % or less of each of a lithium salt of sulfur oxide and lithium N-methylaminobutyrate, and one or more components selected from diphosphorus pentasulfide, elemental phosphorus, and elemental sulfur; rapidly cooling the resultant; and subjecting the resultant to heat treatment, and a high-performance lithium battery using the electrolyte. In particular, the present invention provides a high-performance lithium battery having high energy density, which is obtained by using a positive electrode active material having an operating potential of 3 V or more, a negative electrode active material having a reduction potential of 0.5 V or less, and a lithium ion conductive inorganic solid electrolyte in contact with at least the negative electrode active material, the lithium ion conductive inorganic solid electrolyte being produced from lithium sulfide and one or more components selected from diphosphorus pentasulfide, elemental phosphorus, and elemental sulfur, and which can be used as a monolayer.