In this study, the surface of a silica particle modified with a reactive amino group was developed as an immobilized carrier for use as a biosensor material. Silica particles with a diameter of 5 µm were modified with N-2(aminoethyl)-3-amino-propyl trimethoxysilane as a silane coupling agent at 100 ℃ at heating rates of 2.2, 3.0, and 6.0 ℃/min. These particles were reacted with various concentrations of fluorescein isothiocyanate (FITC) at room temperature for 5 min. FITC-labeled samples exhibited green fluorescence at 520 nm, which was examined by a fluorescence microscope. The fluorescence intensity of a FITC-labeled silica surface was found to increase in two steps with increasing FITC concentration. The rate of increase in fluorescence intensity was higher in Step I than in Step II for all samples. However, the rate of increase in fluorescent intensity in Step I, as well as the amount of reactive amino groups on a silica surface, was strongly affected by the heating rate in the silane coupling reaction. On the basis of these results, conditions of silane coupling reaction and the effect of the conformation of modified amino groups on the silica surface on reactivity were discussed.