A stent delivery device includes a shaft with an internal lumen and a balloon connected to the shaft. The stent delivery device includes a cover configured to advance or retract in the axial direction of the shaft between a covering position where the cover covers the deflated balloon and a retracted position where the cover is spaced apart from the balloon. The stent delivery device includes a drive unit configured to apply a driving force for advancing or retracting the cover. The lumen of the shaft is configured to allow a working fluid to flow through the lumen to inflate the balloon. The balloon and drive unit are operated by the injecting and discharging of the working fluid. The inflation and deflation of the balloon and the advancing and retracting of the cover are performed in conjunction with each other.
