The treatment device comprises an endovenous delivery system (1 2) of at least one dose of therapy, which system of supply (1 2) comprises a wire element (1) of the delivery of a dose of treatment, which is flexible, such as, for example an optical fiber, which has a distal end part (10) able to be inserted, at least a portion of its length, longitudinally into a vein, and which makes it possible to deliver into a vein at least one dose of therapy in the region of the end of said distal end part (10). It also comprises a drive system (4) which makes it possible to cause the wire element (1) of the delivery of a dose in at least a first direction of movement (r), and a guide (3) which is flexible in all or part of its length, and which makes it possible to guide the wire element (1), on a portion of its length, with a proximal end part (11), and on the opposite side, a distal end part (10) of the wire element (1), which are not guided by the guide (3). The device comprises a holding system (5) which makes it possible to temporarily maintain the distal end part (30) of the guide (3) with respect to the body of a patient, in the vicinity of the insertion zone (7) of the wire element (1), and the locking means (6), which make it possible to axially block the proximal end part (31) of the guide (3), at least in the direction of displacement (r) of the wire element (1).Le dispositif de traitement endoveineux comporte un système de délivrance (1 2) dau moins une dose de traitement, lequel système de délivrance (1 2) comprend un élément filaire (1) de délivrance de dose de traitement qui est souple, tel que par exemple une fibre optique, qui a une partie extrême distale(10) apte à être insérée, au moins sur une partie de sa longueur, longitudinalement dans une veine, et qui permet de délivrer dans une veine au moins une dose de traitement dans la région de lextrémité de ladite partie extrême distale (10). Il comprend en outre un système dentraînement (4) qui permet dentra
