A drug injection syringe includes an injection needle assembly and a syringe body. The injection needle assembly includes an injection needle, a needle hub, an elastic body, and a fitting sleeve. The fitting sleeve accommodates the needle hub and the elastic body and has a fitting hole formed in a female taper shape. The syringe body includes an outer tube and a drug discharge tube formed in a male taper shape. The syringe body is attached to the injection needle assembly by pushing the drug discharge tube into the fitting hole by a press fitting. The elastic body couples the drug discharge tube and the injection needle in a liquid-tight manner by compressively deforming, due to the press fitting, at a protruding portion disposed on a periphery of the pocket and stretching against an inner wall of the fitting hole.
