To provide a ventilation block with a strength higher than a certain level capable of giving a ventilating function to a wall body made of mainly glass blocks.

This air ventilation block 1 has a block main body 2 formed to dimensions (height H, width S and depth W) almost the same as those of the outer profile of a glass block for building a wall body by stacking a plurality of the glass blocks, and an air ventilation through-hole is made in a direction perpendicular to the surface of the wall body to be constructed. Also, on the front surface of the ventilation block in the glass block wall, a water stop and vent portion 8 is provided as a louvered window which passes air but not water, and a register type vent volume adjusting portion 14 is provided on the rear surface.