An injection device adapted to the luer lock system and a syringe holder for making it is disclosed. The syringe holder for holding an inserted syringe, with a cap attached to the male luer at the tip, comprises a cylindrical barrel portion having an open distal end and an open proximal end, and a finger rest around the outer surface of the barrel portion at a position relatively closer to the proximal end, wherein a stopper means is provided at the inner surface of the barrel portion at the distal end thereof, the stopper means being designed to abut on the outer edge of the distal end of the syringe, and wherein a female-threaded sleeve extends forwardly from the distal end of the barrel portion, which is designed to surround the tip of the syringe and the cap, and wherein a proximal end cap is provided, at the proximal end of the barrel portion, which is designed to abut on the outer edge of the proximal end of the syringe, and has a bore to pass the piston rod through.