EMBOLIZATION COIL

[Aim] A frame along an inner surface of an aneurysm is stably formed by using a distal end side portion of an embolic coil so that a subsequent embolic coil can be filled smoothly and with good operability into the aneurysm. [Solution] An embolic coil 1 of the present invention is formed by being spirally wound by an element wire and is filled into an aneurysm, and includes: a first coil portion 5, in which a large-diameter coil portion 7 wound to have a large diameter D1 and a small-diameter coil portion 9 wound to have a diameter D2 smaller than the large-diameter coil portion 7 are arranged in a plurality and alternately in a longitudinal direction Y of the embolic coil 1; and a second coil portion 15 wound to be continuous with the first coil portion 5 and to have a surface flatter than the first coil portion 5.