Disclosed is a method for forming lithium hexafluorophosphate by reacting together phosphorus trichloride, chlorine and lithium chloride in a nonaqueous organic solvent and then making the reaction product formed in the solvent react with hydrogen fluoride. This method is characterized by that a lithium hexafluorophosphate concentrated liquid is obtained by conducting a filtration after making the reaction product formed in the solvent react with hydrogen fluoride and then subjecting the filtrate to a concentration by degassing. By this method, it is possible to easily produce a high-purity, lithium hexafluorophosphate concentrated liquid at a low cost.