All-solid-state batteries (ASSB) are recognized as the key to next-generation energy storage technologies and are replacing commercial lithium-ion batteries that use electrolytes composed of flammable organic solvents. Among them, sulfide-based ASSBs have high ionic conductivity and are considered the most promising electrolytes for the next generation of ASSBs. Among various types of sulfide-based electrolytes, argyrodite-based electrolytes have excellent compatibility with lithium metal due to their high ionic conductivity and soft material characteristics, and have received much attention due to their appropriate mechanical properties. However, due to the nature of sulfide-based materials, several issues need to be addressed in order to commercialize them, such as the handling of materials in inert atmosphere and their sensitivity to moisture, instability between interfaces, and limitation of operating potential. Here, the main physicochemical properties of argyrodite-based electrolytes are discussed, and the synthetic methods and electrochemical stability discovered so far are summarized. In addition, we discuss research and development directions for argyrodite-based SSE in several directions.