There has been a need to develop a method for preparing a bread dough using potassium bromate, an excellent bread improver, which provides baked breads free from residual bromate without affecting the flavor and taste of the breads. It has also been desired to develop a method for making breads using such a bread dough. The present invention provides a method for preparing a bread dough, which comprises incorporating potassium bromate as an aqueous solution, in combination with ferrous sulfate and ascorbic acid in the step of forming a sponge dough such that the solubility of the incorporated potassium bromate is increased in the bread dough to facilitate chemical decomposition of bromate, so that the resulting baked breads are free from residual bromate or have a reduced content of residual bromate. Also provided is a method for making breads, which comprises baking the bread dough.