The drug administration device includes a drug container (100), a prefilled syringe (300) including a cylindrical container (310) having a nozzle part (311) and an injection needle mounting part (313), and the inside of the cylindrical container (310). And a connecting device (200) for communicating the inside of the medicine container (100), the connecting device (200) further includes a nozzle insertion portion (240), and the prefilled syringe (300) includes an injection needle mounting portion ( 313) and a cap member (330) having an opening (331a) into which the nozzle insertion portion (240) can be inserted, and an inner peripheral surface of the injection needle attachment portion (313), In the state where the guide groove for guiding the movement of the injection needle is provided and the cap member (330) is fitted in the injection mounting portion (313), at least a part of the edge of the opening (331a) is Than the bottom of the inner groove located inside.薬剤投与具は、薬剤容器（１００）と、ノズル部（３１１）および注射針取付部（３１３）を有する筒状容器（３１０）を含むプレフィルドシリンジ（３００）と、筒状容器（３１０）の内部と薬剤容器（１００）の内部とを連通させる連結器具（２００）とを備え、連結器具（２００）は、ノズル挿入部（２４０）をさらに含み、プレフィルドシリンジ（３００）は、注射針取付部（３１３）に着脱可能に嵌り込むとともに、ノズル挿入部（２４０）を挿入可能な開口部（３３１ａ）を有するキャップ部材（３３０）をさらに含み、注射針取付部（３１３）の内周面には、注射針の移動を案内する案内溝が設けられ、キャップ部材（３３０）が注射取付部（３１３）に嵌り込んだ状態において、開口部（３３１ａ）の縁の少なくとも一部が案内溝の底部よりも内側に位置する。
