To provide a method and an apparatus for manufacturing ammonium biuranate particles which can freely control particle size and can steadily and efficiently manufacture high quality ammonium biuranate particles.

In the method and apparatus for manufacturing ammonium biuranate particle, a raw liquid for manufacturing an ammonium biuranate particle containing uranyl nitrate and a thickener is dropped into an ammonium water solution to form ammonium biuranate particles, the diameter of the raw liquid droplets formed by dropping is measured with a sensor not in contact with the liquid droplets, and the manufacturing conditions are controlled based on the diameter of the measured liquid droplets.