Provided is a method of forming a tin oxide layer using a tin metal target which forms the tin oxide layer on a glass substrate using the tin metal target. The present invention provides the method of forming a tin oxide layer using a tin metal target, which includes forming a tin oxide buffer layer (SnO 2 ) on the glass substrate by sputtering using the tin metal target and forming a tin oxide (SnO 2-x ) semiconductor layer (0 < x ‰¤ 0.01) on the tin oxide buffer layer by sputtering using the tin metal target.