PURPOSE: To enable highly sensitive analysis, by using an ethylene diamine derivative having a P-substitued phenyl group as fluorescent deriving reagent to cause a derivation of a reducing sugar or sialic acid by a simple method.

CONSTITUTION: An eluate 1 is introduced with an eluate feeding pump 2 into a column passage while a sample is introduced into the flow of the eluate with a sample introduction valve 3. After the separation of a reducing sugar in samples with a separation column 4, a deriving reagent solution 5 dissolved in a solvent as reaction liquid and a base solution 6 are added to an eluate passage with a feed liquid pumps 7 and 8 to mix and a reaction is caused with a reaction coil 9. Then, fluorescence of a reactant is measured with a fluorescence detector 10 to be recorded with a recorder 11. Here, a 1,2-dialyl ethylene diamine derivative as deriving reagent is given by the formula of RC(NH2)C(NH2)R, wherein the substituted group R is a p-(or m-) substituted phenyl group such as p-methoxy phenyl.