PROBLEM TO BE SOLVED: To provide an injection needle assembly that can easily connect a syringe to which a needle tube is attached, and a drug injection apparatus using the same.SOLUTION: An injection needle assembly 1 is used by attaching to a syringe 52 having an injection tube 54 filled with a drug and a needle tube 53 and is equipped with a puncturing needle tube 5 having a needle tip 5A that punctures a skin, a needle holding section, an engagement section 32, and a connecting section 14. The needle holding section holds the puncturing needle tube 5, and a fit-in tube 35 of the engagement section 32 engages a needle hub 56 of the injection tube 54. The connecting part 14 has an inner cavity 41 in which a proximal end 5B of the puncturing needle tube 5 opposite from the needle tip 5A and a needle tip (a discharge opening) 53A in the needle tube 53 of the syringe 52 are disposed, and communicates the puncturing needle tube 5 and the needle tube 53 in a liquid-tight manner.SELECTED DRAWING: Figure 5【課題】針管が取り付けられた注射器を容易に接続することができる注射針組立体およびその注射針組立体を用いた薬剤注射装置を提供する。【解決手段】注射針組立体１は、薬剤が充填された注射筒５４及び針管５３を有した注射器５２に装着して用いるものであり、皮膚に穿刺される針先５Ａを有する穿刺用針管５と、針保持部と、係合部３２と、接続部１４とを備えている。針保持部は、穿刺用針管５を保持し、係合部３２の嵌入筒３５は、注射筒５４の針ハブ５６に係合する。接続部１４は、穿刺用針管５の針先５Ａとは反対の基端５Ｂと注射器５２の針管５３における針先（排出口）５３Ａとが配置される内腔部４１を有し、穿刺用針管５と針管５３を液密に連通させる。【選択図】図５
