As for the protector (1), the arm (42) axial support being done the needle itself (15) the needle assembly which it possesses (14) the support component which is installed (18) with, the support component (18) vis-a-vis, the needle itself (15) in direction outside tilt possibly is provided the cover component (36) with, the outside cover component (36) while being provided inside, the cover component (38) with it possesses. The outside cover component (36), the needle itself (15) passes, extending the needle slit which is present (46) the tube body which it has (44) possesses in axial direction. The inside cover component (38), the outside cover component (36) doing, tilt when the needle itself (15) the needle slit (46) being inserted, the needle assembly (14) it is linked, the tube body (44) slides to the inside and the circular arc pillar body which turns (51) it possesses. The circular arc pillar body (51), the tube body (44) the place where the needle slit (46) it opposes at least at the open position for opens, the needle slit (46) it is the section circular arc shape which is closed at blockade position.プロテクタ(1)は、針本体(15)を有する針アセンブリ(14)に装着される支持部材(18)と、支持部材(18)に対してアーム(42)が軸支されて針本体(15)の方向に傾動可能に設けられた外カバー部材(36)と、外カバー部材(36)の内側に設けられた内カバー部材(38)とを有する。外カバー部材(36)は、針本体(15)が挿通し、軸方向に延在する針スリット(46)を備える筒体(44)を有する。内カバー部材(38)は、外カバー部材(36)が傾動して針本体(15)が針スリット(46)に挿入されるときに針アセンブリ(14)に連動し、筒体(44)の内面に摺動して回転する円弧柱体(51)を有する。円弧柱体(51)は、筒体(44)に対する開放位置で少なくとも針スリット(46)に対向する箇所が開口し、閉塞位置で針スリット(46)を塞ぐ断面円弧形である。
