a robot teaching position method for easily modifying an original position of one of a plurality of taught points arranged on a straight line to a modified position moved a distance along the straight line from the original position . an operator selects one of the plurality of taught points , inputs a distance of movement along the straight line from the one taught point to the modified point , and selects two arbitrary taught points arranged on the straight line , using a display device attached to a manual data input device attached to a robot controller . the modified position is determined based on the inputted first taught point , the distance , and the second and third taught points . a robot performs an operation based on the modified position .