To provide a chemiluminescent reagent useful for the identification of amino acid or the like and an amino acid identification method and an amino acid sequence determination method using the same.

This invention relates to a chemiluminescent label agent as given by the formula 1, an amino acid identification method for identifying amino acid labelled by the same and a method of determining the sequence of the amino acid. (wherein R1 and R2 represent lower alkyl group and lower alkenyl group or lower alkoxyl group while terminals of R1 and R2 may be bonded to form a ring and A, lower alkylene residual group or phenylene residual group).