A treatment tool inserting/withdrawing auxiliary device includes: a catheter (6) an operation wire (7) which is inserted into the catheter (6), and is supported on a distal end or the vicinity of the catheter (6) and an operation portion (8) which moves the operation wire (7) back and forth with respect to the catheter (6). The catheter (6) is provided with a curvable portion (16) wherein the distal direction of the catheter (6) is curved with respect to the proximal direction of the catheter (6).
