The recently proposed neutron magnetic tomography, an extension of the three-dimensional neutron depolarization technique, is considered. The new method allows visualization of magnetic domains within bulk materials. In concept it is similar to X-ray tomography but the analysis is much more involved because of the tensorial character of neutron spin rotations. An improved iterative numerical procedure is presented which fully accounts for the non-Abelian properties of the spin rotation. The method is applied successfully to the reconstruction of domain structures from simulated data of schematic examples. The experimental feasibility is discussed.