Disclosed is a method for producing a sulfide solid electrolyte including a step of processing a slurry by at least one treatment selected from drying and heating, wherein a solid electrolyte raw material containing a lithium element, a sulfur element, a phosphorus element and a halogen element, and a complexing agent are mixed in a reactor to give a complex slurry containing a complex formed of the solid electrolyte raw material and the complexing agent, and the complex slurry is transferred into an intermediate tank equipped with a cooling device and cooled therein.