When folded, a balloon (20) in a balloon catheter (10) has a distal end section (24) which has a small outer diameter (D1) and in which a gap (213) between a body part (210) and a wing part (211) is narrow, and a proximal end section (25) which has a large outer diameter (D2) and in which a gap (214) between the body part (210) and a wing part (212) is wide.
