The present invention relates to an occlusion device (1) consisting of a braiding (2) of thin wires or threads (4) which is given a suitable form in a molding and heat treatment procedure. The occlusion device (1) has a proximal retention area (6) and a distal retention area (8), whereby the ends of the wires or threads (4) converge into a holder (5) in distal retention area (8). A cylindrical crosspiece (10) is furthermore disposed between the proximal and distal retention areas (6, 8). With the objective of providing an occlusion device which positions as flat as possible against the septum at the proximal side of a septal defect in the inserted state, the invention provides for the proximal retention area (6) of the braiding (2) to exhibit a completely closed proximal wall (112) disposed with a continuous surface at the proximal end of the occlusion device (1) which forms the proximal end (12) of said occlusion device (1).