Formation of “hill-and-valley” structures on Si(001) vicinal surfaces induced by Au adsorption which accompanies formation of the Si(001)5×3.2-Au reconstruction, was studied by in situ high-resolution low-energy electron diffraction. The “hill-and-valley” structures are composed of (001) terraces and (119) facets under the equilibrium condition independent of the miscut angle (0.5–8°) of the substrate surfaces. This does not depend on sample treatments and the similar structures are obtained by annealing after Au deposition at room temperature as well as Au deposition at high temperature. In situ observation during annealing indicates that commensurate fivefold structures such as 5×3 and √26×3 that were previously observed are not formed on the Si(001) surface and only the 5×3.2 structure is formed in this system. Double domain structures initially formed in such a way that the 5×3.2 and 3.2×5 domains are formed on the 2×1 and 1×2 terraces, respectively, finally transforms into single domain 5×3.2 structure where the fivefold direction is parallel to the miscut direction.