Surface structures of rutile TiO2(001) have been studied by using scanning tunneling microscopy (STM) and first-principles total energy calculations. Prior investigations have observed many kinds of surface structures. However, detailed atomic structure and the common sense of the reconstructions are still unknown. We evaluate the energetical stability of the surface structures. The calculated results suggest that the {111}-microfaceted surface is energetically stabler than the unreconstructed surface. The nature of the reconstruction is explained in terms of microfaceting of the {111} plane, which is consistent with atomically resolved STM images.