Provided is a method for manufacturing a sulfide-based solid electrolyte including preparing a precursor comprising lithium sulfide, germanium sulfide, aluminum sulfide, phosphorus sulfide, and sulfur, conducting a mixing process of the precursor to prepare a mixture, and crystallizing the mixture to form a compound represented by Li9.7Al0.3Ge0.7P2S12. The sulfide-based solid electrolyte may have high ionic conductivity.