One of the two purposes of this study was to execute basic radiation research at Akiyoshido cave, Taishodo cave, and Kagekiyodo cave. The other was to consider the possibilities for teaching materials based on the research results and suggest classes on radiation. After the research, the following two points were clarified. 1. Basically, the interiors of Akiyoshido and Taishodo caves had less radiation than the areas outside the caves. However, it was not clearly stated that the interior of Kagekiyodo cave had less. 2. In Kagekiyodo cave, secondary sediment, with the exception of limestone, was made of lapilli tuff containing radioisotopes. Additionally, limestone did not contain any radioisotope, or an insignificant amount. As a result of the teaching material consideration, we suggest the following classes. Showing the basic radiation research results helps students to understand what kind of radiation tendency each cave has on the inside and the outside. Students can also ponder possible phenomena with regard to the high amount of lapilli tuff radiation and the relatively low amount of limestone radiation amount compared with the background. Additionally, it is possible for students to measure the radiation amounts by themselves on a field trip, and to make an investigation by comparing with the original research results.