The present study has attempted to elucidate the causes of the hydrogen evolution enhanced by the wear process. In this work an open wear-producing system was developed: wear process and hydrogen measuring process were separated from each other, and each process worked successively. The real hydrogen evolution from the specimen exposed to the wear process ocurred more than that from the unexposed specimen even in consideration of the amount of hydrogen both mechanically detached and trapped to the structural defects. The amount of hydrogen evolved due to the wear process was increased with both the time exposed to wear process and the applied normal stress in the wear process. Hydrogen evolution enhanced by the wear process was discussed in terms of the amount of hydrogen evolved as a function of normal stress and the time exposed to the wear process, suggesting that the dislocations generated by the wear process cause the retardation of the hydrogen diffusion due to the trapping of hydrogen in the initial stage of the wear process and the acceleration of the hydrogen diffusion in the later stage where dislocation trap sites are filled with hydrogen to a fixed level.