PURPOSE: To obtain a glass body having increased power of hindering the diffusion of alkali from the glass by forming an alkali diffusion preventing silicon oxide film contg. fluorine bonded to silicon on the surface of glass contg. alkali.

CONSTITUTION: On the surface of glass contg. alkali an alkali diffusion preventing silicon oxide film inhibiting the diffusion of alkali from the glass is formed. At this time, to the silicon oxide film is added fluorine bonded to silicon. The reason that the glass is provided with increased power of hindering the diffusion of alkali from the glass by the silicon oxide film is considered to be that -Si-F bond or -Si-F bond and -Si-H bond are introduced into part of -O-Si-O- bond in the silicon oxide film to make the network structure of the film dense, terminal F or F and H are positively charged to prevent the transfer of alakli ions such as Na+ and K+, and the density difference between the glass and the material of the film coated on the glass surface or an electrical factor is caused, whereby the effusion of alkali ions to the glass surface is prevented.