An ion implanting system and a wafer holding apparatus therefor are provided. The ion implanting system includes x- and y-axis rotating parts; first and second angle measuring circuits; and a controller. The x-axis rotating part rotates a main surface of a wafer about an x-axis, and the y-axis rotating part rotates the main surface of the wafer about a y-axis. The first angle measuring circuit is rotated along with the main surface of the wafer and measures a tilt angle of the main surface of the wafer with respect to the x-axis. The second angle measuring means is rotated along with the main surface of the wafer and measures a rotating angle of the main surface of the wafer with respect to the y-axis. The controlling part, when the measured tilt angles are different from target tilt angles, controls the x- and y-axis rotating parts such that the measured tilt angles are equal to the target tilt angles. In the present invention, the ion implanting system and the wafer holding apparatus therefor can measure and monitor an incidence angle of an ion beam with respect to a tilted wafer.