PROBLEM TO BE SOLVED: To provide a method for inspecting a material containing fine particles easily and accurately.SOLUTION: There is provided a method for inspecting variation in grain size of fine particles in an inspection object containing homogeneous fine particles, the method comprising the steps of: using a liquid in which the fine particles are dispersed in a solvent for electrophoresis using a separation medium which serves as a sieve; and inspecting variation in grain size of the fine particles from an electrophoretic pattern after the electrophoresis.