The present invention relates to an embolus-forming in-vivo indwelling coil in which the direction of action of force being applied to the embolus-forming coil changes by the curvature of the coil when the coil is in-vivo indwelled, such that the coil can be smoothly indwelled without strongly pressing the blood vessel wall of cerebral aneurysm and the coil can be tightly indwelled in the cerebral aneurysm. To accomplish this object, the embolus-forming in-vivo indwelling coil of the present invention has one or more curvatures formed on a unit helical coil of a secondary coil and the curvatures are connected to two angle-changing portions. A method for manufacturing the coil forms the above-described curvatures and the angle-changing portions for the curvatures.
