To provide a stent delivery system that can limit/prevent drop-off or shifting of a stent from the balloon. A stent delivery system that is equipped with a main tube-shaped shaft, a balloon provided on the tip of the main shaft, and a stent fitted so as to encircle the balloon, wherein a layer for preventing stent drop-off containing a compound with multiple thiol groups is formed on at least a portion of the balloon surface, and at least the portion of the stent that contacts the stent drop-off preventing layer is made of metal.