Provided is a drug solution injector that does not leak, reduces dead volume, reduces the amount of remaining drug solution, and efficiently injects a small amount of drug solution into the body. A needle hub 80 that holds the injection needle 90, an elastic body 70 that is placed on the needle hub 80 and through which the injection needle 90 is inserted, and a fitting hole 61 that accommodates the needle hub 80 and the elastic body 70 and has a female taper 63 are opened. An injection needle assembly 50 having a fitting tube 60, an outer tube 30 that seals and stores the drug solution 31, and a drug solution discharge pipe 40 having a male taper 43 that fits into the female taper 63. The syringe body 10 includes the syringe body 10, and the syringe body 10 is connected to the injection needle assembly 50 by inserting the drug solution discharge pipe 40 into the insertion hole 61, and the elastic body 70 is connected to the distal end of the drug solution discharge pipe 40. Is formed on the contact surface side of the dent 73 and is compressed and deformed by the protrusion 72 at the periphery of the dent 73 to be liquid-tightly spread to the inner wall of the insertion hole 61. Connect liquid-tight.液漏れせず、デッドボリュームを低減して残存する薬液量を少なくし、少量の薬液を効率良く体内へ注入できる薬液注射器を提供する。 注射針９０を保持する針ハブ８０と、針ハブ８０に載置され注射針９０を挿通した弾性体７０と、針ハブ８０・弾性体７０を収容し雌型テーパー６３を持つ嵌入孔６１が開いた嵌入筒６０とを有する注射針組立体５０、及び、薬液３１を封止して収容する外筒３０と、雌型テーパー６３へ嵌合する雄型テーパー４３を持つ薬液排出管４０とを、有するシリンジ体１０を、備え、薬液排出管４０を嵌入孔６１へ押し込む嵌入によってシリンジ体１０を注射針組立体５０に接続する薬液注射器１であって、弾性体７０が、薬液排出管４０の先端との接触面側で窪み７３を有し、嵌入により窪み７３の周縁の突出部７２で圧縮変形して嵌入孔６１の内壁へ液密に押し拡げられ、薬液排出管４０と注射針９０とを液密に接続させる。
