In order to investigate the applicability of a thermophoresis dust removal system for fusion plasma devices, the exact estimation of the thermophoretic force acting on discrete dust particle is required. In order to make up for the lack of experimental data, the thermophoretic force acting on a fine spherical particle suspended between the two parallel plates has been measured. In all conventional analyses, it is assumed that the particle is placed and stands still at the center of the confined plates. When the particle is positioned at the center of the plates, the experimental data agrees with the conventional analysis as the asymptotic behavior. On the other hand, when the particle is deviated from the center of the plates, the experimental data shows the different behavior from the analytical formula.