A method for manufacturing a float glass includes a step of melting a glass raw material, a step of forming the glass melted in the melting step into a glass ribbon while floating the glass on a molten metal, and a step of annealing the glass ribbon. In the forming step, a gas or a liquid containing a molecule having a fluorine atom present therein is blown to the glass ribbon having a viscosity of from 1.0×104 to 2.5×1010 Pa·s.