Disclosed therein is a non-reusable and disposable syringe with a plunger rotation preventing structure, in which a gasket serving as a piston is easily separated from a plunger when the plunger is moved backward, thereby preventing reuse of the disposable syringe. The non-reusable and disposable syringe includes an oblong projection formed on a lower plate of the plunger, supporter projections and connectors formed on a gasket supporter, a retaining portion formed on the inner circumference of a tip of a barrel, and a wedge-shaped projection formed on a front end of the plunger corresponding to the retaining portion, so that the connectors are easily broken when the plunger is moved backward after medicine inside the syringe is completely discharged out, whereby it is effectively prevented from being reused.
