Solid electrolyte production method

Provided is a method of producing a solid electrolyte having high ionic conductivity using a liquid phase method, including a first step of mixing two or more compounds satisfying (1) and a complexing agent 1 satisfying (2), and a second step of further mixing in a complexing agent 2 satisfying (3) after the first step. (1) A compound containing one or more selected from a group consisting of a lithium element, a sulfur element, a phosphorus element and a halogen element. (2) A complexing agent capable of forming a complex containing LiPSand a halogen element. (3) A complexing agent other than the complexing agent 1, capable of forming a complex containing LiPS.