Potential of neutron transmission spectroscopy is reviewed from the viewpoints of research and development in magnetism and magnetics. The observation of magnetic Bragg dips requires only the detection of neutron transmitted through a sample along linear narrow path, hence, it has a high affinity for extreme condition-generating devices. This feature is helpful in advancing the frontier in magnetism. On the other hand, the observation of magnetic Bragg edges is useful for measurements of spin arrangements using compact neutron sources because converging optical systems can be utilized without limitation. The resulting opportunities promote to expand the base of magnetism. Furthermore, rectilinearity of the transmitted neutron enables us simultaneous measurements for a plurality of samples that aids high throughput optimization of magnetic materials as well as Bragg edge imaging for magnetic devices. Thus, the neutron transmission spectroscopy is a promising tool in various research field from basic research to practical application of magnetic materials.