An endoscope and an illuminator are safely placed in a body cavity without generating a noticeable postoperative scar. A method of placing medical insertion instruments into a body cavity includes a first step of inserting, into the body cavity through a first opening formed on a body wall, an endoscope together with a first illuminator and a second step of inserting, into the body cavity through a second opening formed at a position different from the first opening, a second illuminator. Preferably, the method further includes a third step of pulling out the first illuminator from the first opening and inserting the first illuminator into the body cavity through a third opening formed at a position different from the first and second openings.
