To provide a glass block which has a high visible light transmittance, a reduced infrared light transmittance, and transparency and thermal insulation properties compatible with each other.

A method for producing a glass block of the present invention comprises formulating a raw material for glass to become borosilicate glass containing, by mass%, 0.01-0.1% Fe₂O₃, melting the glass at 1600 to 1700°C, molding the molten glass into a hollow box shape, and obtaining a glass block having a light transmittance of 90% or more at a wavelength of 550 nm and a light transmittance of 88% or less at a wavelength of 1100 nm in a thickness of 6 mm.