There are some regions where it is difficult to exclude the possibility of appearance of new volcanic activity on the site even if the geological disposal site is located far from existing volcanos in Japan. In order to identify the influence of volcanic eruption at the site to the public if it occurs, public exposure doses were evaluated based on the two scenarios considering types of eruption at new volcanic activity in Japan. One is the exposure by volcanic ash widespread by Strombolian eruption and deposited on the ground surface, including radionuclides from vitrified waste forms after a volcanic conduit penetrated the repository. The other is that by waste forms appeared at the ground surface by Merapi type pyroclastic flow. Exposure doses of the residents living on the volcanic ash do not exceed 1mSv/y even when the eruption occurs at 1,000 years after closure of disposal site. Exposure dose rate for the volcanic researchers temporarily approaching naked waste forms without realizing radioactive wastes is 0.8mSv/h when the eruption occurs 100,000 years after. It indicated that attention should be paid to the influence by Merapi type pyroclastic flow on researchers approaching waste forms appeared rather than that by Strombolian eruption on residents living on the volcanic ash widespread.