TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Material: The sulfide solid electrolyte material includes greater than or equal to 50 mole% of a crystalline phase corresponding to the 2 theta of 20.2 degrees and 23.6 degrees relative to a total crystalline phase of the sulfide solid electrolyte material. Preferred Method: In the method (M1), the ratio of the lithium halide contained in the raw material composition is 14-30 mole% or in a second range in a vicinity of the first range and allows to synthesize the glass ceramics, and an upper limit of the heat treatment temperature is a temperature that allows to synthesize the glass ceramics in a vicinity of 200 degrees C. The heat treatment temperature is less than 200 degrees C (preferably greater than or equal to 170 degrees C, especially less than or equal to 190 degrees C). Preferred Components: The glass ceramics includes an ion conductor containing lithium, element selected from phosphorus, silicon, germanium, aluminum or boron, and sulfur and lithium halide, where the ratio of the lithium halide is 14-30 (preferably less than or equal to 25) mole%. The ion conductor has an ortho composition. EXAMPLE - LiS and P2S5 were measured to be 75Li2S-25P2S5 by mole ratio. Next, Lil was measured so that a ratio of Lil may be 14 mole%. The measured starting raw materials were mixed in an agate mortar for 5 minutes, 2 g of the mixture was charged in a vessel of a satellite ball mill, dewatered heptane was charged in that, further ZrO2 balls were charged in that, and the vessel was completely hermetically sealed. The vessel was installed on a satellite ball mill machine, and the mechanical milling was conducted at 500 revolutions per minute (rpm) of the base for 40 hours. After that, the mixture was dried at 100 degrees C to remove heptane to obtain sulfide glass. Then, 0.5 g of the resulted sulfide glass was charged in a glass tube, and the glass tube was charged in a hermetically sealed SUS vessel. The hermetically sealed vessel was heated at 190 degrees C for 10 hours and glass ceramics (test) was obtained. A molar composition of the resulted glass ceramics corresponds to x=14 in xLil(100-x)(0.75Li2S-0.25P2S5). A comparative glass ceramics were similaraly prepared as test glass ceramics, except that a ratio of Lil in xLil(100-x)(0.75Li2S-0.25P2S5) was changed to x=0, and the Li ion conductivity of the obtained test/comparative glass ceramic was measured by using alternating current (AC) impedance method. The Li ion conductivity (S/cm) of the obtained test/comparative glass ceramics was found to be 2.9x 10-3/1x 10-3 respectively.