To provide an aluminum concentration measuring method for measuring aluminum concentration with high accuracy.

The aluminum measuring method brings a sample including aluminum and a complexing agent into reaction in a buffer solution so as to form an aluminum complex, and measures aluminum concentration in the sample based on the concentration of the aluminum complex in the reacted mixed solution. As a reagent for preparing the buffer solution, one of MES, MOPS, PIPES, HEPES, HEPPSO, EPPS, ACES, ADA or CHES is used. When one of the reagents is used for preparing the buffer solution, aluminum concentrations in the complexing agent and the buffer solution become small, that is, a smaller blank value, thereby measuring the aluminum concentration in the sample with high accuracy.