In a configuration in which the endoscope can be moved forward and backward in conjunction with the advancement and retraction of the treatment instrument, the distal end of the treatment instrument can be easily confirmed while reducing the diameter of the outer tube, improving the surgical efficiency. The present invention provides an endoscopic surgical apparatus and a mantle tube capable of achieving the above. The outer tube (300) inserted into the body wall is provided with an endoscope insertion passage (306) for inserting the endoscope and a treatment instrument insertion passage (308) for inserting the treatment tool. The treatment instrument insertion path (308) is provided in parallel to the reference axis (300a) of (300), and the endoscope insertion path (306) is provided obliquely. Inside the outer tube (300), a slider that engages with the endoscope and the treatment tool inserted through each insertion passage and moves them forward and backward in conjunction with each other moves in the front-rear direction of the outer tube (300). Arranged as possible. The endoscope engaging portion that engages with the endoscope in the slider can also move in the vertical direction, and moves up and down along the position of the oblique endoscope insertion path (306) as the slider moves in the front-rear direction. .処置具の進退移動に連動して内視鏡を進退移動可能とした構成において、外套管の細径化を図りつつ、処置具の先端の状態を容易に確認することができ、手術効率の向上を図ることが可能な内視鏡用外科手術装置、及び外套管を提供する。体壁に刺入される外套管（３００）には、内視鏡を挿通する内視鏡挿通路（３０６）と、処置具を挿通する処置具挿通路（３０８）とが設けられ、外套管（３００）の基準軸（３００ａ）に対して処置具挿通路（３０８）は平行に、内視鏡挿通路（３０６）は斜めに設けられる。外套管（３００）の内部には、各々の挿通路に挿通された内視鏡と処置具とに係合し、それらを連動させて進退移動させるスライダが外套管（３００）の前後方向に移動可能に配置される。スライダにおいて内視鏡と係合する内視鏡係合部は上下方向にも移動可能であり、スライダの前後方向の移動と共に斜めの内視鏡挿通路（３０６）の位置に沿って上下移動する。
