A substrate for an information recording medium, which has high heat resistance and high acid resistance and is formed of a glass having a glass transition temperature (Tg) of 600.degree. C. or higher and having an etching rate of 0.1 .mu.m/minute or less with regard to a hydrosilicofluoric acid aqueous solution that is maintained at a temperature of 45.degree. C. and has a hydrosilicofluoric acid concentration of 1.72% by weight, and an information recording medium having an information recording layer formed on the above substrate.