A process for producing a float bath bottom refractory brick which can suppress a reaction with Na2O from glass at the surface of the refractory brick and thereby prevent flaking phenomena, which process comprises adding a potassium compound to a clayey material comprising from 30 to 45 mass % of Al2O3 and from 50 to 65 mass % of SiO2 and having a Na2O content of at most 1 mass %, so that the K2O content in the float bath bottom refractory brick to be produced would be from 2 to 4 mass %; and a refractory brick useful for a float bath bottom for production of plate glass by a float process.