To provide a valve mechanism of a trocar capable of realizing all of downsizing, reduction in slide resistance at the time of inserting and removing a medical instrument, and prolongation of a service life.SOLUTION: A valve mechanism 10 of a trocar 1 comprises a plate-like first valve 11 and a second valve 12 which abut each other. When inserting/removing a medical instrument 4, while deforming inclined toward the inserting/removing direction of the medical instrument 4 relative to the bottom of a groove 11e as a reference point, the first valve 11 is brought into airtight contact with the outer peripheral surface of the medical instrument 4 at an edge of a through hole 11d. The second valve 12 always closes a through hole 11d in the first valve 11, opens the through hole 11d when the medical instrument 4 is inserted, and abuts against a part of the outer peripheral surface of the medical instrument 4 in the circumferential direction.SELECTED DRAWING: Figure 9【課題】サイズの小型化、医療器具の挿抜時における摺動抵抗の低減、及び長寿命化をいずれも実現することができるトロカーのバルブ機構を提供する。【解決手段】トロカー１のバルブ機構１０は、互いに当接する板状の第１弁体１１及び第２弁体１２を備える。第１弁体１１は、医療器具４の挿抜時、溝１１ｅの底部を基点として、医療器具４の挿抜方向に向かって傾斜した状態に変形しながら、貫通孔１１ｄの縁部で医療器具４の外周面に気密状態で当接する。第２弁体１２は、常時、第１弁体１１の貫通孔１１ｄを閉鎖し、医療器具４の挿入時、貫通孔１１ｄを開放するとともに、医療器具４の外周面の周方向の一部に当接する。【選択図】図９
