It is an object of the present invention to provide: a novel thiol-detecting reagent, which can be used in vivo and which solves the problem regarding the generation of background fluorescence due to hydrolysis and a method for detecting thiol using the aforementioned reagent. The present invention provides a compound represented by the following formula (1):wherein each R2 independently represents an alkyl group containing 1 to 6 carbon atoms, a halogen atom, or a hydrogen atom.
