Abstract: A medical device and a medical device set are disclosed capable of improving passability of a balloon catheter through a body lumen and protection of a balloon. The medical device is an auxiliary device for the balloon catheter, and the medical device has an elongated base shaft, and a distal end member including an extending portion that extends along a longitudinal direction of the base shaft and a balloon protecting portion that is provided on a distal end side relative to the extending portion and is formed in a spiral shape. The balloon protecting portion includes a space portion configured to at least partially accommodate the balloon of the balloon catheter that is provided inward in a radial direction of the spiral shape, and a tapered portion having an outer diameter which decreases toward the distal end side.