An apparatus and method of optimally correcting a static deflection caused by a weight of an end effector coupled to a robot arm or a load on the end effector when the end effector is activated to handle a large sheet of glass. A deflection angle of the end effector is corrected by inserting a compensation member into a joint of the robot arm, and the static deflection caused by the weight of the handling robot when conveying the sheet of glass is also corrected in real time.