A compound is represented by the following general formula (I): The compound or a salt thereof provides a fluorescent probe for detecting carboxypeptidase activity In the formula, R1 represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms; T represents an amino acid residue or a residue of an amino acid derivative; S represents a C-terminal amino acid residue. represents a fluorophore, and the fluorophore is a fluorophore in which an absorption/fluorescence wavelength greatly changes or a quenched state changes to a fluorescent state by elimination of the —P(═O)(—R1)-T-S moiety.