We have determined the contents of monosaccharides in the hydrolysates of some yogurt and orange juice products by derivatizing monosaccharides with p-aminobenzoic acid ethyl ester (ABEE). The separation of the ABEE-derivatized monosaccharides was efficiently carried out by HPLC using a microcolumn packed with the Alltima $C_{18}$ stationary phase. The concentrations of monosaccharides were determined based on the measured peak area/height counts. ABEE derivatization of fructose and its detection have never been successfully carried out before this work. In this study, two peaks were observed in a fixed ratio for ABEE-fructose, and the ratio was maintained over a wide range of fructose concentration. In order to prove the validity of the above method, we compared the concentrations of glucose, galactose and fructose determined by ABEE derivatization and UVD (ultraviolet detector) chromatography with those determined by RID (refractive index detector) chromatography without derivatization. The determined concentrations of monosaccharides obtained from the two chromatographic methods were found close to each other within acceptable error ranges.