A balloon catheter comprising: an outer shaft composed of a resin tube; a balloon connected to the distal end of the outer shaft; a hub connected to the rear end of the outer shaft; an inner tube that is a resin tube inserted into the lumen of the outer shaft and the inside of the balloon and forming a guide wire lumen, the rear end of which opens as a guide wire port on the side surface of the outer shaft, the distal end portion of which is fixed to the distal end portion of the balloon, and the distal end of which opens; and a core wire that has a straight portion and a reduced diameter portion and that is inserted into the lumen of the outer shaft with the reduced diameter portion on the distal end side of the straight portion, characterized in that the core wire is fixed to the inner peripheral surface of the outer shaft on the rear end side of the position where the guide wire port is formed, and the straight portion of the core wire is press-fitted between the inner peripheral surface of the outer shaft and the outer peripheral surface of the inner tube, wherein the distance in the axial direction from the position where the guide wire port is formed to the distal end of the straight portion of the core wire is 1.0 to 50.0 mm, and wherein the cross-section of a part of the outer shaft in which the straight portion is press-fitted is deformed into an elliptical shape by the press-fitting of the straight portion of the core wire, and assuming that the length of the major axis of the ellipse is denoted as (D 11), and the length of the minor axis of the ellipse is denoted as (D 12), the value of (D 11)/(D 12) is 1.02 to 1.30. an outer shaft composed of a resin tube; a balloon connected to the distal end of the outer shaft; a hub connected to the rear end of the outer shaft; an inner tube that is a resin tube inserted into the lumen of the outer shaft and the inside of the balloon and forming a guide wire lumen, the rear end of which opens as a guide wire port on the side surface of the outer shaft, the distal end portion of which is fixed to the distal end portion of the balloon, and the distal end of which opens; and a core wire that has a straight portion and a reduced diameter portion and that is inserted into the lumen of the outer shaft with the reduced diameter portion on the distal end side of the straight portion, characterized in that the core wire is fixed to the inner peripheral surface of the outer shaft on the rear end side of the position where the guide wire port is formed, and the straight portion of the core wire is press-fitted between the inner peripheral surface of the outer shaft and the outer peripheral surface of the inner tube, wherein the distance in the axial direction from the position where the guide wire port is formed to the distal end of the straight portion of the core wire is 1.0 to 50.0 mm, and wherein the cross-section of a part of the outer shaft in which the straight portion is press-fitted is deformed into an elliptical shape by the press-fitting of the straight portion of the core wire, and assuming that the length of the major axis of the ellipse is denoted as (D 11), and the length of the minor axis of the ellipse is denoted as (D 12), the value of (D 11)/(D 12) is 1.02 to 1.30.