The Geographical Survey Institute (GSI) deployed a mobile Very Long Baseline Interferometry (VLBI) system at an established site in Chichijima (the biggest island in the Bonin islands), twice in an interval of two years. Two sessions were conducted in the experiments each year by connecting the reference base station at Kashima Space Research Center of Communications Research Laboratory (CRL). The results from the data of four experiments indicate that the Chichijima site moved 7.4¿0.8 cm in the direction of N67¿W in the two years. This is the first successful direct measurement of the motion of Philippine Sea plate (PHS) by any method. Our result is consistent with the predicted rigid motion of PHS from the newest plate velocity model (NUVEL-1). ¿ American Geophysical Union 1991