A balloon catheter which has an inflatable balloon in a tip end portion, the balloon catheter including: an inner tube which has a main lumen thereinside; and an outer tube which is placed on an outer circumference of the inner tube, and which forms an inflation lumen with the inner tube to flow a fluid for inflating the balloon therethrough, wherein a base end side of the balloon is fixed to the outer tube, whereas a tip end side of the balloon is fixed to the inner tube or the outer tube, wherein a part of the inner tube is coupled to the outer tube at a side of a base end with respect to the balloon, and a side hole is formed in the coupling portion to cause the main lumen to be opened to an exterior, wherein a weakened portion which is lower in rigidity than another portion of the inner tube is disposed on the inner tube at a side of a tip end with respect to the side hole, wherein the weakened portion is configured such that, when the balloon is inflated by the fluid supplied to the inflation lumen, the weakened portion is pressed by a pressure of the fluid to thereby close the main lumen of the inner tube, characterized in that the weakened portion of the inner tube includes: an inner layer which is capable of closing the main lumen by being pressed by the fluid supplied to the inflation lumen; and a reinforcing member which is placed on the outer circumference of the inner layer, and which is configured to allow the fluid to pass therethrough, and wherein the reinforcing member has a gap which allows the fluid to pass therethrough, is placed on the outer circumference of the inner layer without being fixed thereto, and is configured to be separated from the outer circumference of the inner layer when a diameter of the inner layer is reduced. an inner tube which has a main lumen thereinside; and an outer tube which is placed on an outer circumference of the inner tube, and which forms an inflation lumen with the inner tube to flow a fluid for inflating the balloon therethrough, wherein a base end side of the balloon is fixed to the outer tube, whereas a tip end side of the balloon is fixed to the inner tube or the outer tube, wherein a part of the inner tube is coupled to the outer tube at a side of a base end with respect to the balloon, and a side hole is formed in the coupling portion to cause the main lumen to be opened to an exterior, wherein a weakened portion which is lower in rigidity than another portion of the inner tube is disposed on the inner tube at a side of a tip end with respect to the side hole, wherein the weakened portion is configured such that, when the balloon is inflated by the fluid supplied to the inflation lumen, the weakened portion is pressed by a pressure of the fluid to thereby close the main lumen of the inner tube, characterized in that the weakened portion of the inner tube includes: an inner layer which is capable of closing the main lumen by being pressed by the fluid supplied to the inflation lumen; and a reinforcing member which is placed on the outer circumference of the inner layer, and which is configured to allow the fluid to pass therethrough, and an inner layer which is capable of closing the main lumen by being pressed by the fluid supplied to the inflation lumen; and a reinforcing member which is placed on the outer circumference of the inner layer, and which is configured to allow the fluid to pass therethrough, and wherein the reinforcing member has a gap which allows the fluid to pass therethrough, is placed on the outer circumference of the inner layer without being fixed thereto, and is configured to be separated from the outer circumference of the inner layer when a diameter of the inner layer is reduced.