Magnetic circular dichroism in the soft-x-ray absorption spectrum in the 2p→3d excitation region of the transition-metal element is measured for ferromagnetic Cu3Au-type alloys, MnPt3, Fe3Pt and CoPt3 . The electronic state, especially the contribution of the spin and orbital angular momenta to the magnetic moment, is discussed by analyzing the results. The condition for the orbital angular momentum to make a large contribution to the magnetic moment in a metallic system is discussed in terms of the degree of the localization of the 3d orbital, the filling of it, and the symmetry around it.