A method of thinning a glass substrate includes following steps. A glass substrate is provided. A first etching process is performed on the glass substrate, so as to reduce a thickness of the glass substrate. A polishing process is performed on the thinned glass substrate, so that the thickness of the glass substrate is reduced again. A first treated surface is formed on the glass substrate. The center-line average roughness of the first treated surface ranges from about 100 angstroms (Å) to about 300 angstroms (Å). A second etching process is performed on the first treated surface of the glass substrate, so as to form a second treated surface. The center-line average roughness of the second treated surface ranges from about 10 angstroms (Å) to about 50 angstroms (Å).