A substrate transportation path is determined by first determining a trajectory of a first straight line passing through a start point, calculating a trajectory of a circular arc in contact with the first straight line, calculating a trajectory of a second straight line in contact with the circular arc and passing through the end point, then, if the position of the end point is changed, re-calculating the second straight line as a straight line passing through the changed end point and in contact with the circular arc, and allowing the center of the substrate holding unit to move on the first straight line, and then, move on the circular arc from a first contact point, followed by moving on the second straight line from a second contact point so as to reach the end point.