Particularly in the recovery and reuse of unreacted serine after the synthesis of phosphatidylserine by the transfer reaction of a phosphatidyl group with phospholipase D, a simple process for recovering serine in which a material inhibitory to the synthesis of phosphatidylserine can be efficiently removed is provided. The present invention provides the following processes for recovering serine. A process for recovering unreacted serine from a reaction system after the synthesis of phosphatidylserine by the transfer reaction of a phosphatidyl group with phospholipase D, comprising adding a polar organic solvent or a mixture of a polar organic solvent and water to the unreacted serine containing water-soluble fraction in which the phosphatidylserine has been removed from a reaction mixture in the reaction system and washing the fraction with the added solvent or the mixture of the solvent and water to obtain the serine. A process for recovering the serine described above, wherein the synthesis of phosphatidylserine by the transfer reaction of a phosphatidyl group with phospholipase D is performed in an aqueous system in the absence of an organic solvent. A process for recovering the serine described above, wherein the synthesis of phosphatidylserine by the transfer reaction of a phosphatidyl group with phospholipase D is performed in a two-phase system with an organic solvent and water.