An endoscopic surgery device comprising: an endoscope which has an insertion section and observes in a body cavity; a treatment tool which includes an insertion section whose distal end has a treatment portion; and an outer tube (100, 200) into which the insertion section of the endoscope and the insertion section of the treatment tool are inserted, and which guides the insertion section of the endoscope and the insertion section of the treatment tool into the body cavity, wherein the outer tube (100, 200) includes: a cylindrical outer tube body (102, 202) into which the insertion section of the endoscope and the insertion section of the treatment tool are to be inserted; characterized in that the outer tube further comprises: a mobile object (118, 218) provided in the outer tube body (102, 202) so as to be movable in the outer tube body (102, 202) in a direction parallel to an axis of the outer tube body (102, 202); an endoscope holding section (126, 226) which is provided in the mobile object (118, 218) and holds the insertion section of the endoscope inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202); and a treatment tool holding section (124, 224) which is provided in the mobile object (118, 218) and holds the insertion section of the treatment tool inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202). an endoscope which has an insertion section and observes in a body cavity; a treatment tool which includes an insertion section whose distal end has a treatment portion; and an outer tube (100, 200) into which the insertion section of the endoscope and the insertion section of the treatment tool are inserted, and which guides the insertion section of the endoscope and the insertion section of the treatment tool into the body cavity, wherein the outer tube (100, 200) includes: a cylindrical outer tube body (102, 202) into which the insertion section of the endoscope and the insertion section of the treatment tool are to be inserted; characterized in that the outer tube further comprises: a mobile object (118, 218) provided in the outer tube body (102, 202) so as to be movable in the outer tube body (102, 202) in a direction parallel to an axis of the outer tube body (102, 202); an endoscope holding section (126, 226) which is provided in the mobile object (118, 218) and holds the insertion section of the endoscope inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202); and a treatment tool holding section (124, 224) which is provided in the mobile object (118, 218) and holds the insertion section of the treatment tool inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202). a cylindrical outer tube body (102, 202) into which the insertion section of the endoscope and the insertion section of the treatment tool are to be inserted; characterized in that the outer tube further comprises: a mobile object (118, 218) provided in the outer tube body (102, 202) so as to be movable in the outer tube body (102, 202) in a direction parallel to an axis of the outer tube body (102, 202); an endoscope holding section (126, 226) which is provided in the mobile object (118, 218) and holds the insertion section of the endoscope inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202); and a treatment tool holding section (124, 224) which is provided in the mobile object (118, 218) and holds the insertion section of the treatment tool inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202). a mobile object (118, 218) provided in the outer tube body (102, 202) so as to be movable in the outer tube body (102, 202) in a direction parallel to an axis of the outer tube body (102, 202); an endoscope holding section (126, 226) which is provided in the mobile object (118, 218) and holds the insertion section of the endoscope inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202); and a treatment tool holding section (124, 224) which is provided in the mobile object (118, 218) and holds the insertion section of the treatment tool inserted into the outer tube body (102, 202) parallelly to the axis of the outer tube body (102, 202).