The advancement of science and technology is always accompanied by better manufacturing precision. Ideally, the highest precision for manufacturing a surface is truly atomic flatness, which implies that all topmost surface atoms are in a single layer of the crystal face. However, almost no methods can achieve this surface with high efficiency at present. Herein, we present a method to fabricate a large-scale truly atomically flat surface with ultrafast speed. Through the selective etching of surface atoms, our method can achieve an atomically flat surface with 0.05 nm Sa roughness. It is notable that the polishing efficiency of our method is more than 1000 times higher than that of conventional methods. We have demonstrated its generality on various single-crystal materials and obtained atomic roughness and an ultrahigh polishing rate. This method has the potential to promote the mass-production of atomic-scale smooth surfaces, the application of third-generation semiconductor materials, and the innovation of advanced technologies.