Manual injection device comprising a lower body (1) receiving a reservoir (S), said reservoir being axially displaceable with respect to said lower body (1) and containing fluid to be injected, said reservoir (S) comprising a piston (P) ) and a needle (A), an upper body (2) axially displaceable with respect to said lower body (1) during actuation, said upper body (2) comprising a piston rod (TP) cooperating with said piston (P ) during the injection to move it in the tank (S), a sleeve (10) movable relative to said lower body (1) between a rest position, wherein said sleeve (10) is disposed inside said lower body (1), and a projected position, in which said sleeve (10) is axially displaced out of said lower body (1), said sleeve (10) being locked in its rest position before actuation of the manual injection device and being asked automatically in its projected position after injection, said piston rod (TP) defining with said reservoir (S), or with any element integral with said reservoir (S), an actuation lock, comprising a stitching component and a component of injection, the force required to actuate said stitching component being less than the force required to actuate said injection component, so that said stitching is performed before said injection. Dispositif d'injection manuelle comportant un corps inférieur (1) recevant un réservoir (S), ledit réservoir étant axialement déplaçable par rapport audit corps inférieur (1) et contenant du produit fluide à injecter, ledit réservoir (S) comportant un piston (P) et une aiguille (A), un corps supérieur (2) axialement déplaçable par rapport audit corps inférieur (1) lors de l'actionnement, ledit corps supérieur (2) comportant une tige de piston (TP) coopérant avec ledit piston (P) lors de l'injection pour le déplacer dans le réservoir (S), un manchon (10) déplaçable par rapport audit corps inférieur (1) entre une position de repos, dans laquelle ledit manchon (10) est disposé à l'intérieur dudit corps inféri
