This device is intended to receive an injection syringe. The injection syringe has: a syringe body, a piston mounted slidably in the syringe body, and an injection needle fixed to a distal end of the syringe body. The automatic injection device includes a piston control member, which is displaceable in translation with respect to the syringe body, parallel to an axis X, in order to control the displacement of the piston in the syringe body, a piston rod intended to push a proximal end of the piston of the injection syringe, releasable coupling means for coupling the piston control member and the piston rod, an injection spring which bears on the piston control member and elastically stresses the piston control member towards a distal end of the injection needle. The releasable coupling means are positioned axially between the two axial ends of the injection spring.
