Endoscopic surgical device and overtube

An endoscopic surgical device comprising:

• an endoscope that observes the inside of a body cavity;
• a treatment tool that inspects or treats an affected part within the body cavity;
• and
• an overtube that guides the endoscope and the treatment tool into the body cavity,
• wherein the overtube includes
• an overtube body that passes through a body wall and is inserted into the body cavity,
• an endoscope insertion passage that is provided inside the overtube body and allows the endoscope to be inserted therethrough so as to be movable forward and backward,
• a treatment tool insertion passage that is provided inside the overtube body and allows the treatment tool to be inserted therethrough so as to be movable forward and backward, and
• an interlocking member that is configured to be movable forward and backward inside the overtube body and has an endoscope-coupled part coupled to the endoscope inserted through the endoscope insertion passage and a treatment tool-coupled part coupled to the treatment tool inserted through the treatment tool insertion passage, the endoscope-coupled part has a through hole being the endoscope insertion passage and the treatment tool-coupled part has a through hole being the treatment tool insertion passage, and
• wherein during ordinary use of the endoscopic surgical device a following formula is satisfied when a first fixing force for fixing the endoscope-coupled part to the endoscope at a fixed position of an outer peripheral surface of the endoscope is defined as F1 and a second fixing force for fixing the treatment tool-coupled part to the treatment tool at a fixed position of an outer peripheral surface of the treatment tool is defined as F2, F1 is a magnitude of the first fixing force with respect to an axial direction of the overtube body, and F2 is a magnitude of the second fixing force with respect to the axial direction of the overtube body:
• F1>F2.