PURPOSE: To find the positional deviation of a wafer handling arm from the programmed position data so as to enable the arm to transfer a wafer correcting the position of the handling arm on the basis of the data concerned by a method wherein a holding support used for mounting a wafer support on a handling arm main body is formed into a spherical seat bearing structure, and a load detecting element is provided to each quarter part divided with the holding support as its center.

CONSTITUTION: The tip of a holding support 3 is formed into a spherical seat bearing structure, and a wafer support 1 is able to move vertically or laterally a little making the holding support serve as a support point. The deviation of the programmed delivery point from the groove of an actual wafer cassette occurs, a force is applied to the wafer support 1 when a downward force is applied to a wafer 7, a load is added to a load detecting element 2a located closer to the wafer than the holding support, and on the contrary, a load on a load detecting element 2b located behind the holding support 3 is reduced. As a load detecting element is arranged at each of quatered parts in a lateral direction, the direction of a force applied to the wafer support 1 is detected, and the detected direction of force is fed back to a handling drive section to adjust the position of all the arm.