A superconducting alloy containing magnetic impurities, which may become magnetically ordered, is considered. It is found that an antiferromagnetic order is favoured. However, when the superconducting and magnetic transition temperatures are close to each other a large concentration of nonmagnetic impurities causes the spontaneous magnetization to be uniform in the vicinity of both transition temperatures. The Landau-Ginzburg free energy functional for this case is calculated and the phase diagram is discussed. We find that for sufficiently strong exchange and spin-orbit scatterings there appears a mixed phase of the two order parameters.