A catheter can efficiently transmit an operator's pushing force to a distal end of the catheter with a reduced risk of getting caught at a curved region of a lumen (e.g., a blood vessel, bile duct, pancreatic duct or the like). The catheter includes a first core wire and a second core wire disposed between an inner tube and an outer tube. The second core wire can move to an optimal position depending on external forces exerted at a curved region of the lumen when the catheter is inserted into the curved region. Therefore, there is a reduced risk that the first core wire and the second core wire will interfere with each other, which would prevent the catheter from bending along the lumen and potentially break one or both of the first core wire and the second core wire.
