The present investigation attempts to evaluate the improvement of working by bolt on the fatigue limit of structural steel sheets with drilling a circular hole. The material used in this study is structural steel (JIS SM400A). And the specimens are identified to two types of the non-worked specimen and the worked specimen. The results obtained in this study can be summarized as follows: (1) The fatigue limit of worked specimens increases than that of non-worked specimen. Futhermore, there has a suitable value of the torque for improving the fatigue limits. (2) The reasons of enhancing the fatigue strength of the worked specimens are due to the elastic deformation, the plastic deformation and the changing of stress concentration part. Our investigations confirm the advantages of this working method which repaired the structural steel sheets by bolt.