An operating unit in a stent delivery system comprises a displacement body including a first body connected to an outer tube body and a second body which is connected to the first body and meshed with a rotary roller. A first connection surface of the first body is formed with a first convex portion and a first concave portion recessed relative to the first convex portion. The first convex portion engages a second concave portion of the second body and a second convex portion engages the first concave portion. When movement of the displacement body becomes difficult for some reason and the operator forcibly rotates the rotary roller, the engaged state of the second body and the first body is released and the second body is relatively moved, thus preventing movement of the first body in the axial direction.