Provided a method of producing a glass having a silica skeleton with a phase-separated structure, particularly in the case of a phase-separated glass, by selectively removing a compositionally deviated layer on the surface of a phase-separated borosilicate glass. The method of producing a glass includes forming a glass body containing silicon oxide, boron oxide, and an alkali metal oxide; and bringing an alkaline aqueous solution having a viscosity of 5 mPa·s or more to 200 mPa·s or less into contact with a surface of the glass body.