PROBLEM TO BE SOLVED: To provide a fish body injection device allowing even a non-expert to quickly inject vaccine without injuring a fish body.SOLUTION: A fish body injection device includes: a syringe 2 including an injection cylinder, a needle 12 connected to the tip of the injection cylinder, and a piston inserted into the injection cylinder drive means 3 driving the piston in the axial direction of the injection cylinder a guide member 4 provided in front of the syringe, for bringing a fish body into contact with it displacement detection means 5 connected to the guide member, bringing the fish body into contact with the guide member, and detecting displacement of the guide member when having inserted the needle into the fish body and control means 6 driving the drive means on the basis of output from the displacement detection means.
