An injection needles assembly body is constructed so that the residual amount of drug is decreased under a condition that it is unnecessary to precisely adjust the position, relative to the needle hub, of the base end of a needle pipe. The injection needles assembly body 2 includes a needle pipe 5, with a needle point 5A to pierce the skin； a needle hub 6； and an elastic member 7. The needle hub 6 has a first member 11 for keeping the needle pipe 5； and a second member 12, in which the removal portion 52 of a syringe 3 is embedded. The elastic member 7 is arranged inside the second member 12 and liquid-tightly jointed to the inner side of the second member, and has an insertion-through hole 45 inserted through the needle pipe 5.一種注射針組合體，以無需精密地對針管的基端相對於針插座的位置進行調整的構造來使藥劑的殘存量減少。注射針組合體2包括具有穿刺至皮膚的針尖5A的針管5、針插座6、以及彈性構件7。針插座6包括保持著針管5的第1構件11、以及嵌入有注射器3的排出部52的第2構件12。彈性構件7配置於第2構件12的內部且液密地密著於上述第2構件的內表面，該彈性構件7具有使針管5插通的插通孔45。
