The injection device (1) comprising:a container (5)a housing (9)a piston (7)a plunger rod (40)automatic injection means (24)retaining means, at least partly formed on the housing (9) and arranged to maintain the container (5) in the insertion position, anddeactivating means, formed on the proximal part of the plunger rod (40) and arranged to release automatically the retaining means and cause the container (5) to move to the final position,wherein, when the piston (7) comes into contact with the distal end of the container (5), under the force exerted by the automatic injection means (24) on the proximal part of the plunger rod (40), the distal part of the plunger rod (40) is thereby stopped and the proximal part of the plunger is allowed to continue its distal movement under the force exerted by the automatic injection means (24) for a certain time until the deactivating means cooperate with the retaining means to cause the container (5) to move from the insertion position to the final position.
