An embolization device which is placed at a definite position in a vessel cavity in vivo to embolize the vessel cavity. More specifically speaking, an embolization device to be used for plugging a blood vessel or a aneurysm formed in a blood vessel. After being placed in a vessel cavity in vivo, this embolization device promotes not only thrombosis but also organization over the surrounding area, thereby exerting an excellent embolization effect on the vessel cavity. Namely, an embolization device for plugging a vessel cavity in vivocharacterized by having biological response modifiers (BRM) which can promote organization and exert an enhanced embolization effect after being placed in a vessel cavity in vivo.
