A simple method is proposed to detect a gel structure using a light‐scattering technique. A sample in a cylindrical cell was rotated in a typical dynamic light‐scattering setup. The measurements were made on a solution of gelatin in which polystyrene latex spheres were added as the light‐scattering probes. When the solution became a gel state, the light intensity observed at a fixed scattering angle showed a large fluctuation during rotation of the sample. The amplitude of the fluctuation was found to be a good measure of the gel structure.