A process for treating a radioactive liquid waste is disclosed, in which a radioactive liquid waste containing uranium and .beta.-decay nuclides, daughter nuclides of uranium, is treated by combination of a flocculation method using water glass as pretreatment and a subsequent ion exchange method. An approximately total amount of the uranium and a part of the .beta.-decay nuclides, daughter nuclides of uranium, in the liquid waste are captured by an amorphous silica precipitate formed by addition of the water glass and a remaining part of the .beta.-decay nuclides, daughter nuclides of uranium, is captured thereafter by the ion exchange treatment. The thus captured radioactive materials are respectively eluted from the filtered out precipitate, a radioactive solid waste, and the ion exchanger by acid treatment to be recovered as an acidic solution. Thus, the radioactive materials in the liquid waste are recovered approximately completely, thereby making the radioactivities of a final drain remarkably reduced. The precipitate is then dissolved in an alkali metal hydroxide solution to make the amorphous silica constituting the precipitate regenerated to water glass.