The present disclosure relates to a polypeptide including an Fc-gamma receptor mutant. The Fc-gamma receptor mutant of the present disclosure is optimized by substituting a part of an amino acid sequence of an Fc-gamma receptor with a different amino acid sequence, so as to provide an excellent selective binding ability to immunoglobulins. Therefore, it can be usefully used for increasing in vivo half-life of drugs, detecting and purifying immunoglobulins, inhibiting organ transplant rejections, or preventing or treating autoimmune diseases.