The present disclosure relates to a method of producing a solid electrolyte with a uniform particle size distribution and a spherical shape. The method includes preparing a raw material comprising one or more of a lithium (Li) element, a phosphorus (P) element, or a sulfur(S) element, preparing a starting material comprising the raw material and a solvent, obtaining an intermediate in powder form by spray drying the starting material, and obtaining a sulfide-based solid electrolyte by heat treating the intermediate.