In the paper the existence of a solution to the three dimensional elastoplastic problem with the Prandtl-Reuss constitutive law and the Neumann boundary conditions is obtained. The proof is based on a suitable combination of the parabolic regularization of equations and the penalty method for the elastoplastic yield condition. The method is applied in the case of the domain with smooth boundary as well as in the case of an interior crack. It is shown that the weak solutions to the elastoplastic problem satisfying the variational inequality meet all boundary conditions.