A catheter is provided that is capable of achieving an improvement in operability when the catheter is introduced into a human body. A guide wire port 21 is formed in a midway position, in an axial line direction, of a peripheral wall portion 23 of an outer shaft 15 of a balloon catheter 10. A core wire 30, which extends across the guide wire port 21 in the axial line direction is provided in an outer tube hole 15a of the outer shaft 15. The core wire 30 is provided with a leading end side area 31, which is further to a leading end side than the guide wire port 21, and a tapered area 32, which is provided on a base end side of the leading end side area 31. The tapered area 32 is provided continuously from the base end side of the leading end side area 31 and has a first tapered area 34, which includes a same position as the guide wire port 21 in the axial line direction, and a second tapered area 35, which is provided continuously from a base end side of the first tapered area 34. A rate of increase of a transverse cross-sectional area from the leading end side toward the base end side is larger in the first tapered area 34 than in the second tapered area 35.
