In a chemical surface modification, effects of modified conditions on adhesive force were investigated. As test samples, propyl-modified plates were prepared by 36 different modified conditions on Si plates. The surface free energy and surface roughness of the modified plates were measured. Furthermore, adhesive forces between the modified plates and unmodified silica particle were measured by an AFM colloidal probe technique. As a result, the energy, the roughness and the force were 24.8～54.8 mJ/m2, 0.04～56.0 nm and 0.78～7.32 mN/m, respectively. The contribution ratio of each factor on the adhesive force was investigated by multiple regression analysis. From this result, a hydrophilic treatment （＝ pretreatment of the modification） had a highest contribution. This is because a type of hydrophilic treatment generated the differences of surface roughness and hydrophilic property of the Si plate. Molecular structures of propyl chain in the modified layer might be also changed by these differences and affect the adhesive force.
