FIELD : medicine. SUBSTANCE : invention relates to medical technology, namely to automatic injection devices. Apparatus comprises : housing configured to hold a drug container with a needle, the housing includes an angled ridge; needle shield, which is slidably disposed in the housing and adapted to move from the extended position relative to the housing in which the needle is closed, to the abduction position relative to the housing in which the needle is open and back, the needle shield comprises a first flush of the shield; piston slidably disposed in the housing and displaced relative to the housing by means of a drive spring, with the ability to direct the force of the drive spring to the stopper in the drug container, the piston contains a piston tide. Tide of the piston rests against the edge when the piston is displaced relative to the rib for turning the tide of the piston, the first tide of the casing is positioned with the ability to abut against the tide of the piston and prevent its disengagement from the angled edge, when the first tide of the casing is aligned with the angled edge in the extended position of the needle casing, and where the tide of the piston disengages from the rib when the needle shield is in the retracted position, thereby disrupting the axial alignment of the first flush of the casing with the piston tide the way the piston tide rotates due to its displacement in the distal direction in the direction of the angled rib, so that the piston tide is detached from the edge passing at an angle, allowing the piston to move along the axis relative to the body, characterized in that the edge passes at an angle relative to the longitudinal axis of the body and reports the rotational and axial force to the tide of the piston. EFFECT : object of the present invention is to provide an improved autoinjector. 12 cl, 7 dwg