An endovascular treatment aiding device with which adhesion of the endovascular treatment aiding device to a blood vessel can be confirmed, and which can prevent leakage of a captured substance, is disclosed. The endovascular treatment aiding device is an endovascular treatment aiding device comprising: a flexible shaft； a filter fixed to the shaft such that an opening section is formed in the proximal side, wherein a ring having elastic restoring force is fixed to the opening section, which filter is capable of being opened and closed in an umbrella-like manner, and is in a conical shape having a bottom formed by the ring when the filter is open； and a linear supporting member fixed to the ring and a part of the shaft such that these are connected to each other, which linear supporting member enables to close the filter by application of an external force to the proximal side； wherein coils formed with a radio-opaque material is/are wound around the ring； when the filter is closed, a plurality of mountains pointing toward the distal side and a plurality of valleys pointing toward the proximal side are alternately formed in the ring to form a shape in which the mountains are positioned close to each other, and the valleys are positioned close to each other； and the coils are arranged on the ring such that the coils contain the positions fixed by the supporting member on the ring, but do/does not contain the positions of the peaks of the mountains and the peaks of the valleys.
