Method for manufacturing glass plate with which warping during chemical strengthening is reduced and glass plate

Provided is a method for manufacturing a glass plate which is capable of effectively suppressing warps after chemical strengthening and of omitting or simplifying polishing treatment, etc. before chemical strengthening. The present invention relates to a method for manufacturing a float glass plate which comprises a step of melting a glass raw material, a step of forming a glass ribbon while floating glass that is melted in the previous step on molten metal, and a step of annealing the glass ribbon, wherein the float glass plate comprises 63 to 73% of SiO2, 0.1 to 5.2% of Al2O3, 10 to 16% of Na2O, 0 to 1.5% of K2O, 5 to 13% of MgO and 4 to 10% of CaO (mol%), in the forming step, a top face which opposes a bottom face that contacts the molten metal in the glass ribbon is subjected to a dealkalization treatment for 1 to 30 seconds in a float bath, and the surface temperature of the glass ribbon during the dealkalization treatment is 600 DEG C or more.