Provided are a method of preparing a graft copolymer, a graft copolymer, and a thermoplastic resin molded article. The method of preparing a graft copolymer includes 1) adding a conjugated diene-based monomer and performing polymerization to prepare a conjugated diene-based polymer; and 2) adding the conjugated diene-based polymer, an aromatic vinyl monomer, and a vinyl cyan monomer and performing polymerization to prepare a graft copolymer, wherein an emulsifier having an APHA color value of 50 or less and a critical micelle concentration of 1 to 50 g/l is added, so that excellent polymerization stability, colorability, light resistance, and surface clarity are exhibited.