The purpose of this study was to clarify whether function differs between the first toe and the second to fifth toes in terms of single-leg standing balance ability. Cluster analysis was conducted using the peak value (P) and the delay time at which P occurs regarding the cross-correlation function as variables. The first toe and the second to fifth toes had different functions regarding the movement of the center of pressure (COP) in the medial-lateral direction. The first toe had the function of moving the COPin the lateral direction of the foot, whereas the second to fifth toes had the function of moving the COP in the medial direction of the foot. On the other hand, regarding the movement of the COP in the anterior-posterior direction, all toes had the function of moving the COP in the posterior direction of the foot.