PURPOSE: To automatically install an elastic annular body on a work by holding the elastic annular body by the outer peripheral surface of a sleeve by the contraction of itself, applying the sleeve on the work, and pulling out the elastic annular member from the sleeve and fitting the elastic annuler body on the work.

CONSTITUTION: As a mandrel 1 is inserted into the inside diameter part of an elastic annular body 4, the elastic annular body 4 is shifted to a sleeve 2, being pushing-spread by the tapered outer peripheral surface of the blade 1b of the mandrel 1, and held by the contraction of itself. A holding device 106 is shifted in the X-axis direction of a robot 109 and positioned directly over a work 110, and the Z-axis arm 105 of the robot is lowered, and the lower edge surface of the mandrel 1 is positioned through the contact with the upper edge surface of the work 110, and when the stepped part 2b on the inner peripheral surface of the sleeve 2 contacts the large diameter part of the work, and the lowering of the sleeve 2 stops, only an outer cylinder 3 lowers, and the elastic annular body 4 is pushed down and slipped off from the sleeve 2, and fitted into the fitting part of the work 110 by the contraction of itself.