To realize a technology that prevents impairment of coaxiality after inserting a compressive member R into a clearance S by removing an inner ring W1 and an outer ring W2 from a mounting device, can suppress a product tolerance within a allowable tolerance only by mounting, and does not require finishing cutting after the mounting.

A rubber mounting device 20a is a device for mounting a rubber R to the clearance S existing in work W, and comprises a drag 26 for positioning the work W, a cope 24 movable between an abutting position and a separating position from the positioned work W, and a hydrostatic pressurizing device (a constant pressure valve 60, a pump 58, a motor 56, or the like). The cope 24 has a cope groove 33 for storing the rubber R at the position facing to the clearance S, and an extruding member 45 for moving the rubber R from the position facing to the clearance S into the clearance S. The clearance S of the work W and the cope groove 33 for storing the rubber R are blocked from the external field when the cope 24 abuts on the work W positioned by the drag 26, and the hydrostatic pressurizing device applies hydrostatic pressure to the cope groove 33 blocked from the external field.