Neutron shielding materials and spent fuel container.

A material neutron shielding containing epoxy resin as one of its main components, comprising a hardened material which is prepared by mixing a base resin which contains a compound including two or more epoxy groups in the molecule as at least one component, with a hardener for opening said epoxy rings and polymerizing thereof at a temperature higher than room temperature, wherein hardened material contains a fire retardant that said base resin contains.