To provide a glass block of which the heat insulating gel layer has transparency, and wherein a through hole due to the fallout of a glass surface is not generated even at the time of a fire, and which has a fire protecting performance.

The heat insulating gel layer is formed on the internal side of at least one translucent surface for this glass block having the fire protecting performance. In this case, the heat insulating gel layer contains a gelling agent comprising one or two kinds or more of inorganic polymerizers selected from a group comprising a colloidal silica, an alumina sol and a zirconia sol, and a mixture of one kind or two kinds or more selected from a group comprising an inorganic acid, an organic acid, an inorganic acid salt and an organic acid salt. Also, the mass ratio of the inorganic polymerizer/the gelling agent for the heat insulating gel layer is 30 to 300.