We investigated theoretically the influence of the transport current and applied magnetic field on the magnetostriction of type-II superconductors. In order to study the magnetostrictive response of a superconducting slab specimen, three cases of magnetic history of the sample are considered in the present work: (1) the transport current applied after zero-field-cooling, (2) the current and field are applied simultaneously, (3) the current is applied at the remenent critical state. In the proposed model, the exponential critical state model and the Bean model is employed to compute the flux profile within the slab subjected to sufficiently small transport current and applied magnetic field. Simple expressions for the internal stress and the magnetostriction in terms of this magnetic profile are derived. The magnetostriction curves versus the transport current and applied field are presented.