The invention relates to an injection device comprising a housing, a container holder arranged within said housing, the container holder being configured for accommodating a medicament container having a needle attached to one end thereof and a stopper sealingly and slidable arranged inside the medicament container at the other end thereof, a plunger rod being arranged with a proximal end thereof contactable with said stopper, a first and a second energy accumulating member arranged in the interior of the housing of the injection device and adapted to accumulate and store energy, plunger drive means being slidable arranged in relation to the plunger rod, being rotationally locked to the plunger rod and being rotatable in relation to the housing, the plunger drive means being operationally associated with the first energy accumulating member, a container driver arranged for being connectable to the container holder and threadedly connected to the plunger rod, the container driver being operationally associated with the second energy accumulating member such that due to an output axial force from the second energy accumulating member, the container holder and the plunger rod are axially moveable in relation to the housing a predetermined distance towards the proximal end of the injection device from an initial locked position to a second position whereby a needle penetration is performed, wherein the plunger drive means are locked from being rotated by the container driver, and wherein the plunger drive means are released such that due to an output torque from said first energy accumulating member, the plunger drive means are allowed to be rotated and the plunger rod is urged towards the proximal end of the injection device whereby an injection is performed.