A body insertion instrument has an inserting portion inserted into a body near a target organ as a target of surgery. The body insertion instrument further includes a space securing unit, disposed to the inserting portion, configured to secure a space, in which the target organ is operated on, one of between the target organ and an organ different from the target organ and between the target organ and one of an abdominal wall and a chest wall, and a drive unit configured to drive the space securing unit for acting force the one of between the target organ and the organ different from the target organ and between the target organ and the one of the abdominal wall and the chest wall.
