[en] For magnetic structure refinement of bulk materials, the neutron diffraction technique is the most reliable probe. In this short article, basic information of magnetic structure refinement by powder neutron diffraction; in particular, actual process of data analysis will be presented with real data. First, the author will explain some typical commensurate and incommensurate structures, and how the structure represent by propagation vector k, which is the one of the most important value for magnetic structure refinement. The author will show the magnetic structure factor, and explain the meanings of each factor of which the magnetic structure factor consists. Each process from neutron diffraction experiments to the analysis for practical magnetic structure refinements will be explained in the case of the rare earth compound TmB₂C₂. In the section, information on some diffractometers in Japan which are suitable for magnetic structure refinements will be given. Finally, information on some important and powerful analysis softwares for Rietveld analysis and a quite sophisticated technique, the representation analysis technique, will be presented. (author)