Disclosed is a method of disposal of metallic aluminum-containing solid waste comprising the steps of reacting radioactive solid waste containing metallic aluminum with an alkali solution to generate a hydrogen gas and then mixing the resulting reaction liquid with a solidifying material containing a latent hydraulic material as a main component to solidify the liquid. According to the method of the invention, solidification of aluminum-containing radioactive solid waste in a highly filled state (high concentration) is feasible and a solid having excellent mechanical strength and properties of preventing oozing of radioactive nuclide can be obtained.