A new approach to describe the cyclic plastic deformation of a carbon steel was presented by applying and extending the cyclic plasticity model proposed by the authors in the previous paper, based on the random barriers theory. The field of resisting force against the movement of dislocations regulating the stress-strain curve in each half cycle could be expressed by using the density function given by a composite Weibull distribution having a parameter of division which was named in this paper as the border stress. As a result of discussions with some experiments, it was clarified that the cyclic hardening or softening behavior of a carbon steel under constant strain cycling tests, both in the initial stage and in the case after the strain range increases or decreases in the steady stage could be described by a unique rule based on the change characteristics of the force field depending on the stress and strain history.