<p>An indwelling instrument for forming an embolus capable of being securely indwelled at a specified position, securely allowing the re-indwelling thereof even after temporarily indwelled, and accordingly capable of providing high safety and high operability, comprising a flexible coil body, wherein an axial extension restriction member with a specified tensile break strength is installed in the coil body so as to be extended in the axial direction of the coil body. The axial extension restriction member is characterized by comprising a wire material having a tensile break strength of 700 N/mm<2> or higher in the axial direction of the coil body and a diameter of 25 mum or less.</p>
