An automatic injection device including an injection spring deformable between a compressed state prior to use and a relaxed state after injection. The device includes a plunger control member configured to apply a force to a plunger under the action of the injection spring to allow the plunger to move in the distal direction of the device. The plunger control member bears a stop that is retractable between an active configuration in which it retains the injection spring in the compressed state and a retracted position in which it releases the injection spring. The device also includes a locking member for locking the retractable stop in its active configuration, this locking member being able to adopt a locking position in which it applies pressure to the retractable stop to prevent it from adopting its retracted configuration, and an unlocking position in which the retractable stop is released.
