The purpose of this study was to investigate the factor of determination of the center of gravity of the right and left axis in sitting of hemiplegic patients. Subjects were 30 hemiplegic patients. The subjects center of gravity point was measured during 1) natural sitting, 2) sitting on the non-paretic weight-bearing, and 3) sitting on the paretic weight-bearing under eyes open and eyes closed conditions for ten seconds. We calculated the middle point value for 2) and 3), and observed a correlation between the center of gravity point during natural sitting and the middle point. This result indicate that the center of gravity point is decided by relative position of the maximal voluntary weight-bearing of the non-paretic and paretic sides.