The present invention relates to an injection device comprises a generally elongated tubular housing having opposite proximal and distal ends； a needle shield sleeve slidably and coaxially arranged inside the housing and protruding a distance outside the proximal end of the housing； a syringe carrier mechanism comprising a syringe carrier slidably and coaxially arranged to the needle shield sleeve, wherein said syringe carrier comprises a syringe having a medicament and a needle； a first activator member slidably and coaxially arranged to the housing and connected to said needle shield sleeve； an actuating member slidaby and coaxially arranged to the first activator member； a drive mechanism slidably and coaxially arranged to the actuating member and to the syringe carrier mechanism, said drive mechanism being controlled by the actuating member； a second activator member slidably and coaxially arranged to the distal end of the housing and fixedly connected to the actuating member； wherein the first and the second activator members are coaxially movable relative each other from a non-activation position wherein the activator members are abutting to each other to an activation position wherein the activator members are co-acting independent of the sequence in which said activator members are activated； and wherein only in the activation position is the actuating member capable of releasing the drive mechanism to move said syringe carrier mechanism for penetrating the needle and to deliver said medicament through the needle.一種注射裝置，係包括一普通瘦長管狀外殼有相對的近端和末端；一針頭保護套可滑動的且同軸地配置於外殼內，且伸出外殼近端一距離；一針筒承載機制包括一針筒載具可滑動且同軸地配置於針頭保護套，在此該針筒載具包括一針筒有一藥物和一根針；一第一啟動構件可滑動且同軸地配置於外殼且連接於該針頭保護套；一驅動構件可滑動且同軸地配置於第一啟動構件；一驅動機制可滑動且同軸地配置於驅動構件和針筒承載機制，該驅動機制被驅動構件控制；一第二啟動構件可滑動且同軸地配置於外殼末端且固定連接於驅動構件；在此第一和第二啟動構件可從非啟動位置(在此啟動構件互相鄰接)相互同軸移動至啟動位置(在此啟動構件共同獨立一連串動作，該啟動構件被啟動)；且在此只有於啟動位置時，驅動構件能夠鬆開驅動機制來移動該針筒承載機制使針穿刺並經由針來輸送藥物。
