A method of producing a sulfide solid electrolyte and a method of producing an electrode mixture are described. The method of producing the sulfide solid electrolyte includes a step of mixing a raw material inclusion containing a lithium atom, a phosphorous atom, a sulfur atom, and a halogen atom with at least one lithium oxoacid salt of lithium nitrate, lithium nitrite, lithium silicate, lithium borate, and lithium carbonate. The sulfide solid electrolyte has high ion conductivity and excellent reactivity with an electrode active material, especially a positive electrode active material.