The invention provides a hand function evaluating method based on the position change of each hand portion in a three-dimensional space. The hand function evaluating method includes the steps of starting an evaluating system, placing a hand in the system, obtaining real-time video information, obtaining a three-dimensional spatial position, determining the position of the palm center of an injured hand, changing the coordinate of the injured hand, unitizing the coordinate of the injured hand, selecting a standard hand, calculating the distance between the injured hand and the standard hand, calculating the distance from each portion of the injured hand to the center of the palm, calculating the distance between the standard hand and the injured hand, determining the position of a palm center of a healthy hand, changing the coordinate of the healthy hand, unitizing the coordinate of the healthy hand, calculating the distance between the injured hand and the healthy hand, calculating the distance from each portion of the healthy hand to the center of the palm, calculating the distance between the healthy hand and the injured hand, estimating according to the measured distance from each hand position to the palm center, estimating the injured hand by calculating the distance between the injured hand and the healthy hand and the standard hand, calculating the hand function data of the injured hand, and completing assessment of the injured hand.