The present invention is to provide a method for cleavage of peptidic bond at C terminal of peptide and a method for determination of C terminal amino acid sequence of peptide without the decrease of the sensitivity and with preventing the subsidiary reaction. The method for cleavage of peptidic bond at C terminal of peptide according to the present invention is characterized as follows: A method for cleavage of peptidic bond at C terminal of peptide comprising the steps of: reacting a peptide with a solution of perhalogenated carboxylic acid containing alcohol to esterify glutamic acid residue of said peptide; and reacting said peptide with alkanoic acid anhydride to obtain C terminal-deleted peptide in which the amino acid residue of said peptide at C terminal is sequentially deleted. The method for determination of C terminal amino acid sequence of peptide according to the present invention is characterized as follows: A method for determination of C terminal amino acid sequence of peptide comprising the steps of: reacting a peptide with a solution of perhalogenated carboxylic acid containing alcohol to esterify glutamic acid residue of said peptide; reacting said peptide with alkanoic acid anhydride to obtain C terminal-deleted peptide in which the amino acid residue of said peptide at C terminal is sequentially deleted; measuring molecular weight of said C terminal-deleted peptide; and grasping said peptide based on said molecular weight.