Abstract: One embodiment provides a balloon catheter which has an inner tube having a main lumen and an outer tube which forms an expansion lumen. A part of the inner tube is connected to the outer tube at a position closer to the proximal end than a balloon, a side hole is open at the connection section, and a weak section is provided to the inner tube a position closer to the distal end than the side hole. The weak section has lower rigidity than the remaining portion of the inner tube. When the balloon is expanded by fluid supplied to the expansion lumen, the weak section is pressed by the fluid pressure to thereby close the main lumen of the inner tube.