While the period of high growth of Japanese economy, infrastructures were actively constructed. Now the structures are aged and its evaluation of integrity is one of significant topics to keep its serviceability and safety in Japan. Although the authors have been studied on tomographic techniques that are on the basis of elastic wave propagation for the evaluation, elastic wave difficultly propagate inside of structures if the structures are covered by stiff materials, e.g. steel reinforcement, and evaluation of integrity of the structures is difficult as consequence. Further, electromagnetic waves have been widely used for the inspection of concrete structures as well. However, dissipation rate of the electromagnetic waves is generally high in metals, and it is also difficult to penetrate inside of the structures. On the other hand, neutron beam is known as a radioactive ray which permeability is high and it would be applicable for the inspection of inside of the concrete structures. Thus, in this study, permeability of neutron beams to concrete specimens is discussed as preliminary study for establishing the inspection technique of concrete structures with neutron beam.