When it advanced the cap in order to make the inside needle lock, the compound needle which does not have a possibility the inside needle advancing is developed. Outside possesses the tubular base in the basic edge inserting from the rear end of the needle and the tubular base, while making extend from the point of the needle outside the description above, the flange which was formed to the peripheral aspect of the axial direction intermediate section with the compound needle which possesses the needle, compared to it forms the insertion section in the front, in the rear end, about the back it inserts the insertion section of the lock component which possesses the slit where the taper surface and the tube wall where major diameter becomes small are cut off to axial direction in the tubular base from the rear. Turning the cap, when it makes come forward on advanced side, the taper surface of the aforementioned lock component entering into the taper concave section of the aforementioned cap, reduction diameter it does the hole of the part where the said taper surface is formed and while passing, it tightens the needle and becomes lock state, but because as for the lock component the flange this touching to the rear end surface of the tubular base, there are no times when it advances, the inside needle opposing to mind, there are no times when it advances.内針をロックさせるためにキャップを前進させた場合、内針が前進するおそれのない複合針を開発する。基端に筒状基部を有する外針と、筒状基部の後端から挿入して前記外針の先端部から突出させる内針を有する複合針で、軸方向中間部の外周面に形成されたフランジ部よりも前方に挿入部を形成し、後端部に、後側ほど外径が小さくなるテーパ面と、筒壁が軸方向に切断されたスリットを有するロック部材の挿入部を筒状基部に後方から挿入する。キャップを回して先端側に進出させると、前記ロック部材のテーパ面が前記キャップのテーパ凹部に入り込んで該テーパ面が形成されている部分の挿通孔を縮径し挿通した内針を締め付けてロック状態となるが、ロック部材はフランジ部が筒状基部の後端面に当接して前進することがないので、内針が意に反して前進してしまうことがない。
