Provided is a bendable treatment instrument that enables an individual doctor who is performing an endoscopic procedure to reliably and intuitively manipulate forceps, a knife, or the like. A bendable treatment instrument (1) includes a mechanism connecting, via a flexible tube body (4) encasing a transmission member, a bending section (3) configured to perform a bending action and a manipulation member (8) configured to receive a manipulation with respect to the bending section (3) from an operator. The mechanism is capable of transmitting a manipulation by the manipulation member (8) to the bending section (3). The bendable treatment instrument further includes a support member (7) configured to support the manipulation member (8) while clasping the flexible tube body (4), and a rotation support member (11) configured to support the manipulation member (8) so as to allow the manipulation member (8) to axially rotate with respect to the flexible tube body (4) at the support member (7).
