Abstract: A stent device which can be loaded on any balloon catheter and which permits an arbitrary stent to be employed in combination with an arbitrary catheter. That is, the present invention is directed to a stent device having a stent fitted on the outer peripheral surface of a radially dilatable and contractible tubular cartridge. The stent device is mounted on a balloon-forming portion of a balloon catheter designed for extending the outside diameter of the catheter from a contracted state to a dilated state. The balloon-forming portion is dilated in the vessel for dilating the stent along with the tubular cartridge. The balloon-forming portion and the tubular cartridge are then contracted for detaching the stent from the balloon catheter for supplying the stent within the vessel.