The endovenous treatment device has a delivery system (1; 2) for delivering of at least one treatment dose, which delivery system (1; 2) includes a wire element (1) for delivery of a treatment dose, which has a distal end part (10) able to be inserted, over at least part of its length, longitudinally into a vein, and which allows at least one treatment dose to be delivered into a vein in the region of the end of said distal end part (10). It additionally includes a drive system (4) by which the wire element (1) for dose delivery can be driven in at least a first given drive direction (R), and a guide (3) which is flexible along all or part of its length. The device includes a holding system (5) by which the distal end part (30) of the guide (3) can be temporarily held with respect to the body of a patient, near the insertion zone (7) of the wire element (1).