Endoscopic surgery device

An insertion part of an endoscope and an insertion part of a treatment tool, which are inserted in an outer tube, can be synchronously moved in the axial direction, and, even when the insertion part of the treatment tool is slightly moved in the axial direction, an excellent endoscopic image without shake is obtained. When a treatment tool of an endoscopic surgery device moves by a displacement amount over an allowance amount, an endoscope moves in interlock with the movement of the treatment tool. Moreover, the treatment tool 50 moves in the axial direction with the allowance amount t with respect to the endoscope 10. Therefore, when the treatment tool is moved by a displacement amount of allowance amount or less, the endoscope does not move. By providing such allowance amount, slight movement of the treatment tool is not transmitted to the endoscope.