In the present study, to examine the effects of somatosensory stimulation of the hands on the hand functions and visuomotor coordination of children with developmental disabilities, a total of 24 sessions of experiments were conducted with three children with developmental disabilities for 60 minutes per session, three sessions per week from January 7, 2013 to March 11, 2013. To examine the effects of somatosensory stimulation of the hands on grasping and visuomotor coordination which are sub-areas of PDMS-2, the A-B study design was used which is a single case study method out of single-subject experimental research designs. Somatosensory stimulation of the hands was shown to be effective in improving the hand functions of children with developmental disabilities. Somatosensory stimulation of the hands showed positive effects on the raw scores and standardized scores of grasping and visuomotor coordination in all the three subject children. Visuomotor coordination functions showed higher scores in post-hoc tests in all three children. In particular, ring throws showed high scores at right $90^{circ}$, right $45^{circ}$, center, left $45^{circ}$, and left $90^{circ}$ among visual directions. In the present study conducted with children with developmental disabilities, ring throws were performed to examine visuomotor coordination. In particular, the numbers of successes of ring throws on the front, left, and right were shown to be high. Therefore, somatosensory stimulation of the hands was effective on the hand functions and visuomotor coordination functions of children with developmental disabilities.