The invention provides a glass-making process of conducting vacuum defoaming without bumping; a glass-making process of conducting vacuum defoaming without making blisters remain in glass articles, which blisters result from the enlargement of a foam layer; and a glass-making process of conducting vacuum defoaming while inhibiting the vaporization of specific components (such as boron) contained in molten glass. A glass-making process which comprises the step of vacuum -defoaming molten glass in a vacuum defoaming tank, wherein the water vapor concentration of the atmospheric gas in the tank is controlled to be 60% by mole or below.