An operating unit constituting a stent delivery system is provided with a first rotary roller having a first gear and a second rotary roller having a second gear. The first gear is meshed with a first tooth portion of a rack member and the second gear is meshed with a second tooth portion of the rack member. The first gear is formed to have a large diameter relative to the second gear and at the time of releasing a stent, after positioning a distal end of an outer tube body close to the stent through the rack member with the rotation of the first rotary roller of the operating unit, it is possible to move the outer tube body toward a proximal side at a lower speed than that in the previous state with the rotation of the second rotary roller.