Provided is a treatment device including a long, thin inserted portion having a channel that penetrates in the longitudinal direction a forceps portion that has a pair of holding pieces that can be opened and closed at the distal end of the inserted portion and a piercing needle that is accommodated in the channel and that is provided with a through-hole into which a guide wire can be inserted, extends in the longitudinal direction to a needle-tip face, wherein the first holding piece can be disposed at a position shifted toward the proximal end from the distal end of the second holding piece, and the piercing needle can be made to stick out from the opening at the distal-end surface of the inserted portion into a space formed between the distal ends of the pair of holding pieces, which are disposed shifted from each other.
