To provide a method for smoothing a surface of a glass substrate having a concave defect, such as a pit or a scratch.A method for smoothing a surface of a glass substrate having a concave defect thereon, comprising: forming a film on the surface of the glass substrate having the concave defect by a dry deposition method, the film comprising a glass material having a fluid point Tf of 150° C. or above and of not higher than a strain point Ts (° C.) of the glass substrate; and heating the film of the glass material at a temperature of not lower than Tf and not higher than Ts to put the film in such state that the film of the glass material can flow so as to bury the concave defect, followed by cooling the film of the glass material, thereby to smooth the surface of the glass substrate having the concave defect.