Provided are a method of preparing retinal ganglion cells by differentiation of stem into retinal ganglion cells, retinal ganglion cells differentiated by the method, a method of screening for a death inhibitor or a proliferation promoter of retinal ganglion cells using the retinal ganglion cells differentiated by the method, a kit of screening for the death inhibitor or the proliferation promoter of retinal ganglion cells including the retinal ganglion cells differentiated by the method, a pharmaceutical composition for treating glaucoma or optic neuropathy including the retinal ganglion cells, a method of treating glaucoma or optic neuropathy including the step of administering the retinal ganglion cells to a subject suspected of having glaucoma or optic neuropathy, and a method of preparing a mature retinal ganglion cell line.