Abstract: A catheter for removing foreign substances in a blood vessel includes a catheter main body and an expansion part that is provided spaced from a front end of the catheter main body at a predetermined front end distance and expands a contour of the catheter, and is particularly suitable to be inserted from downstream of the bloodstream. The side face of the catheter main body has a side hole for suction within the area of the front end distance. It is advisable that the catheter has a plurality of holes which are provided equally spaced centering an extension axis of the catheter main body (at symmetrical positions on a cross section vertical to the extension axis). The catheter for removing foreign substances in a blood vessel capable of preventing outflow of foreign substances downward from the part to be treated is provided.