The purpose of this research is to investigate the micro-mechanism of anelastic behavior of metallic glass. The changes of atomic arrangement in Cu50Zr50 metallic glass were observed directly by EXAFS method during tensile deformation. The transmission-mode EXAFS measurements around Zr K-edge and Cu K-edge of the sample in various amounts of tensile deformation conditions were done. The interatomic distance between Cu-Zr increased, and that between Zr-Zr decreased simultaneously, with the amount of tensile deformation increase of the sample at first stage of deformation. When the atomic distances reached to certain values respectively, they recovered to the initial values of no tensile deformation condition at first stage, and then the atomic distances changed as same manner as the first stage of deformation, respectively. This is the first observation on the change of atomic arrangement during tensile deformation of metallic glass.