An operation device, a mantle tube, an endoscope, and a treatment instrument having a simple structure and good operability are provided. The mantle tube 100 is provided with a slider 140 inside the mantle tube main body 102. When the endoscope 10 and the treatment instrument 60 are inserted into the mantle tube 100, they are held and integrated with the endoscope holding section 148 and the treatment tool holding section 146 provided with the slider 140. As a result, when the treatment tool 60 is moved in the axial direction, the endoscope 10 moves in the axial direction in conjunction with this movement. In the mantle tube 100, the inner diameter of the endoscope opening type air-tight valve portion 138 provided in the valve member 120 is larger than the inner diameter ID 4 of the elastic member 156 provided for holding the endoscope 10 in the endoscope holding portion 148 Is also set to be large. This makes it easy to insert and eject the endoscope 10 into the mantle tube 100.簡単な構成で操作性のよい手術装置、外套管、内視鏡及び処置具を提供する。外套管100は、外套管本体102内にスライダ140を備える。内視鏡10と処置具60は、外套管100に挿入されると、スライダ140の備えられた内視鏡保持部148と処置具保持部146とに保持されて一体化される。これにより、処置具60を軸方向に移動させると、これに連動して内視鏡10が軸方向に移動する。外套管100は、弁部材120に備えられる内視鏡用開口型気密弁部138の内径が、内視鏡保持部148で内視鏡10を保持するために備えられる弾性部材156の内径ID4よりも大きく設定される。これにより、外套管100への内視鏡10の挿抜作業を容易に行うことができる。
