PROBLEM TO BE SOLVED: To provide a catheter capable of smoothly transmitting push-in force from the hand side to the tip side, and thereby improving operability thereof.SOLUTION: A shaft 12a of a catheter 10B includes: a small-diameter part 24a provided on the tip side； a large-diameter part 26 provided on the base end side with respect to the small-diameter part 24a； and a taper part 28 provided between the small-diameter part 24a and the large-diameter part 26. The small-diameter part 24a includes: a first small-diameter part 50 adjacent to the tip side of the taper part 28； and a second small-diameter part 48 which is adjacent to the tip side of the first small-diameter part 50, has an outer diameter larger than that of the first small-diameter part 50, and is more flexible than the first small-diameter part 50.
