Provided is a sulfide-based solid electrolyte which is capable of suppressing the generation of hydrogen sulfide caused by reaction with moisture even when in contact with dry air in a dry room or the like, and capable of maintaining lithium ion conductivity. Proposed is a sulfide-based solid electrolyte for a lithium secondary battery, wherein the surface of a compound containing lithium, phosphorus, sulfur, and halogen, and having a cubic argyrodite-type crystal structure is coated with a compound containing lithium, phosphorus, and sulfur, and having a non-argyrodite-type crystal structure.