A method for processing a radioactive liquid waste containing boron of the present invention includes: a molar ratio control step of adding an alkali metal or an alkali metal compound to a radioactive liquid waste containing boron to control an alkali metal/boron molar ratio in the radioactive liquid waste to be 0.8 or more; a drying step of drying the radioactive liquid waste having the controlled molar-ratio using a dryer to form a powdered waste; a dissolving step of mixing the powdered waste with kneading water to prepare a solution; and a kneading step of adding a hydraulic inorganic solidifying material to the solution, and kneading the hydraulic inorganic solidifying material and the solution for solidification.