To provide a thermal treatment apparatus for a glass substrate of high production efficiency in spite of a low-cost energy-saving type.

In this thermal treatment apparatus A for a glass substrate, the glass substrates 2 which are heated bodies, can be enclosed and disposed in multiple stages in a box-shaped heating furnace body 1, and heaters 3 are disposed almost on the whole inside of the heating furnace body. In this constitution, an air agitation fan 50 is provided at a sidewall on one side of the heating furnace body.