PROBLEM TO BE SOLVED: To provide a method for producing a sulfide-based solid electrolyte which can accurately control the elemental composition of a sulfide-based solid electrolyte without waste of a raw material resource.SOLUTION: There is provided a method for producing a sulfide-based solid electrolyte which comprises a step of bringing a first sulfide-based solid electrolyte and at least one selected from the group consisting of an alkali metal sulfide, a sulfur compound, elemental sulfur, elemental phosphorus, a halogen compound and a second sulfide-based solid electrolyte having an elemental composition different from the first sulfide-based solid electrolyte into contact with each other to produce a third sulfide-based solid electrolyte having an elemental composition different from the first sulfide-based solid electrolyte and the second sulfide-based solid electrolyte.
