Abstract: A balloon catheter includes a hollow shaft having a lumen through which an expansion liquid flows, and an expandable and contractible balloon arranged so as to cover at least a part of an outer periphery of the hollow shaft. The hollow shaft has an opening that communicates between the lumen and an inside of the balloon, and an outer peripheral surface of the hollow shaft has a groove extending across the opening and along the outer peripheral surface.

Abstract: A catheter having a shaft including a first lumen that communicates from the proximal end to the distal end of the shaft, and a second lumen that is positioned on the outer periphery side of the first lumen, communicates from the proximal end side to the distal end side of the shaft, and has a smaller opening area than the opening area of the first lumen in a transverse section of the shaft. The dimension in the first direction in the distal end portion of the shaft where the first lumen and the second lumen are aligned is less than or equal to the dimension in the first direction in the proximal end portion that is closer to the proximal end side than the distal end portion of the shaft.