This paper discusses wear phenomena from an aspect of the atomic interaction. It is demonstrated that the friction coefficient is affected difference in the inter-atomic distances between the mutually rubbed materials. Then, from the relation between the friction coefficient and wear coefficient, it is discussed that progress of wear is strongly affected by the number of atoms subjected sheer force simultaneously. The lager difference in inter-atomic distances represents the lower friction coefficient and the smaller wear. It is almost impossible to remove one atom from the surface during a wear process, because applied force to the atom is much weaker than the supporting force around the atom.