A catheter enabling an increase in operability when the catheter is inserted from the outside to the inside of a body and capable of remarkably reducing the risk of damage to shafts even in an unforeseen accident without complicating steps and increasing production cost. The catheter comprises at least the distal side shaft formed of a resin tube, the rear end side shaft with a higher rigidity than that of the distal side shaft, and a guide wire lumen. The catheter is characterized in that a core wire is disposed therein to adjust a flexibility so that the rear end portion of the distal side shaft is harder than the distal end portion of the distal side shaft and softer than the rear end side shaft, and the core wire is fixed to the distal side shaft near the rear end side opening part of the guide wire lumen and at a part of the rear end side portion of the distal end shaft.