In 2020, Super-Kamiokande introduced Gadolinium sulfate into the detector for the first observation of Diffuse Supernova Neutrino Background (DSNB). For the DSNB search, we have to precisely estimate the atmospheric neutrino background, however, it has still large uncertainty because the reaction of neutron with a few hundred's of MeV via oxygen nucleus is poorly understood. We conducted the experiment, named E525, which measure the reaction of neutrons with oxygen, at the Research Center for Nuclear Physics, Osaka University on October 30, and December 16, 2018. This is an experiment, which neutrons with 250 MeV and 30 MeV are irradiated to water target, and gamma rays emitted from the reaction were measured. In this presentation, the results of this experiment will be presented.