We investigate the atomic structure of the tungsten ditelluride (WTe2) surface by using low-energy electron diffraction (LEED), scanning tunneling microscopy, and density functional theory (DFT) calculations. From the LEED and DFT analyses, we find small but non-negligible surface relaxation that gradually decays in an oscillatory manner inside the first WTe2 layer. In addition, the DFT calculations reveal that the Fermi surface topology is sensitive to this relaxation. These results are helpful for understanding the exotic properties of WTe2. (C) 2017 The Japan Society of Applied Physics