[Problem] To provide a dosing instrument capable of administering a drug solution even when a tip opening of a cannula is obstructed. [Solution] A dosing instrument 200 is connectable to a drug solution dosing device 100 provided with a drug solution container 110 filled with a drug solution. The dosing instrument 200 is connectable to the drug solution dosing device and has: a connecting part 210 formed with an inner cavity 210a that is communicable with an inner cavity 111 of the drug solution container when connected to the drug solution dosing device； a cannula 220 that has a tip opening 220a and is punctured into a living body； and a puncture part 230 that includes a contact surface 231 for coming into contact with a body surface H, a cannula-holding part 232 for holding the cannula so that the tip of the cannula protrudes from the contact surface, and a communication passage 233 that communicates with an inner cavity 220b of the cannula and the inner cavity of the connecting part. The cannula has a thin-walled section 250 which is formed in a part in the circumferential direction θ of the cannula closer to a base end than the tip opening is and closer to the tip than the contact surface is, and which is provided with a wall thickness smaller than that of other parts of the cannula except for a tip part 231, the thin-walled section cleaving when subjected to pressure equal to or greater than a set pressure.Le problème décrit par la présente invention est de fournir un instrument de dosage capable d'administrer une solution médicamenteuse même lorsqu'une ouverture de pointe d'une canule est obstruée. La solution selon l'invention porte sur un instrument de dosage (200) qui peut être relié à un dispositif de dosage d'une solution médicamenteuse (100) pourvu d'un récipient de solution médicamenteuse (110) rempli d'une solution médicamenteuse. L'instrument de dosage (200) peut être relié au dispositif de dosage d'une solution médicamenteuse et présente : une partie
