Abstract: A method of mounting a contactor comprising: a step S10 of recognizing a reference point on a mount base; a step S12 of recognizing the positions of first marks on the mount base to calculate the actual relative position m1 of the first marks with respect to the reference point; a step S13 of calculating a theoretical relative position m0 in design of the first marks with respect to the reference point; a step S14 of calculating the relative amount of deviation ?m of the actual relative position m1 with respect to the theoretical relative position m0; a step S22 of recognizing the positions of first marks in the mounting system; a step S23 of specifying the mounting position of the contactor on the mount base on the basis of the amount of deviation ?m and the position of the first marks; and steps S27 and S28 of mounting the contactor at the mounting position.