Provided is an indwelling catheter which is stiff when being inserted into a vessel such as a blood vessel, softens after indwelling in the vessel, and conforms to a shape in a direction in which the vessel runs. In the indwelling catheter, the maximum value of a catheter repulsive force in a dry state at 25° C. is 0.10 N or more； the maximum value of the catheter repulsive force when immersed in warm water at 37° C. is 0.01 to 0.25 N； a ratio of the maximum value of the catheter repulsive force in a dry state at 25° C. to the maximum value of the catheter repulsive force when immersed in warm water at 37° C. is in a range of 3.5:1 or more； and the maximum value of the catheter repulsive force when immersed in warm water at 37° C. is 0.027 N or less after 5 minutes from indwelling.
