A kind of syringe of what is closed in this creation comprising an injection tube, a needle set group and a push rod. The injection tube includes that injection tube one end collects section, which encloses one room of structure. The needle set group includes an adapter, a needle stand and a syringe needle, the adapter separatably sets what, and this collects in section and internal is equipped with a buckle slot, the adapter includes a cylinder part and an elastic plug member, the elasticity plug member is equipped with the buckle slot, the elasticity plug member socket what cylinder part one end and separatably abut what this collect section, the needle stand is arranged the what adapter, which sets the other end of the what needle stand far from the adapter. The push rod includes an elastic piston and an ejector, which slippingly sets inside the what injection tube, and one end of the ejector, which wears the what elastic piston and extends, has set a Hook arm, the Hook arm system elastically deformable. Wherein, when the push rod collects , Hook arm system and buckle slot phase clip when section sliding Qie Hook arm is inserted into the buckle slot towards this, using can pass through the ejector and pulls in the needle set group in the injection tube.本創作關於一種注射器，其包括一注射筒、一針具組及一推桿。該注射筒包括一位於該注射筒一端之收束段，該注射筒圍構一容室。該針具組包括一轉接頭、一針座及一針頭，該轉接頭可脫離地設於該收束段中且內部設有一卡扣槽，該轉接頭包括一筒件及一彈性塞件，該彈性塞件設有該卡扣槽，該彈性塞件套接於該筒件之一端且可脫離地抵接於該收束段，該針座被套設於該轉接頭，該針頭設於該針座遠離該轉接頭之另一端。該推桿包括一彈性活塞及一推頂件，該彈性活塞可滑移地設於該注射筒內部，該推頂件之一端穿設於該彈性活塞且延伸設有一鈎臂，該鈎臂係可彈性變形。其中，當該推桿朝該收束段滑移且該鈎臂插入該卡扣槽中時，該鈎臂係與該卡扣槽相卡掣，藉以可透過該推頂件將該針具組拉入該注射筒中。
