A safety syringe mainly comprises an injection needle, a barrel and a sleeve. The injection needle is sleeved to the needle holder at the front end of the barrel. The sleeve is sleeved on the outer edge of the barrel. The outer edge of the barrel has at least one guide rail and the surface of the inner sleeve wall has a tenon at or near the end of the sleeve. After completing the action of injection or injection solution drawing, the sleeve is pushed toward the front end of the barrel to cover the injection needle by the sleeve. Further, the retention surface of the tenon is made to be abutted against the retention surface of a plurality of serrations disposed on one side or both sides of the guide rail, so that the sleeve cant be pushed back to prevent the sharp end of the injection needle from exposure to achieve the purpose of avoiding needle pricking condition from occurring.一種安全針具,主要包括一注射針、一針筒及一套管,該注射針係套於該針筒前端之針座上,該套管為套設於該針筒外緣,該針筒之外緣具有至少一導軌,該套管末端或接近末端之內管壁表面具有一卡榫,當注射或取液之動作完成後,係將套管向針筒之前端推動,使套管將注射針包覆住,並透過卡榫之榫滯留面與該導軌一側或兩側所設複數鋸齒之滯留面相抵頂,而使套管無法推退,以防止注射針之尖銳端外露,達到避免針扎狀況發生之目的。1‧‧‧針筒11‧‧‧針座12‧‧‧導軌121‧‧‧鋸齒1212‧‧‧導入面1213‧‧‧滯留面122‧‧‧第一段導軌123‧‧‧第二段導軌124‧‧‧第三段導軌2‧‧‧套管3‧‧‧預留槽4‧‧‧注射針
