Safety syringe having a restrictively rotatable plunger

A safety syringe comprises a barrel having a grip lug with two fitting holes and two retaining holes communicating with each other; an elastic lashing member capable of retracting elastically and inwards, and having two locating pillars which are provided with an arresting head being retained in the retaining holes of the barrel, two slide confining portions being disposed at each side; a plunger having two slide pieces; a needle holder being caught and pulled by the plunger, and fitting a needle set. In use, the slide pieces of the plunger are confined by the slide confining portion of the elastic lashing member such that the plunger can not be turned. The plunger arrives at the bottom in the wake of injection such that the plunger is not confined by the elastic lashing member, and that the plunger can be thus turned to actuate the needle holder and drawn into the interior of the barrel by the plunger.