[Problem] To provide 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.[Solution] In this 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 3.5 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.
