The present invention relates to a syringe, and more particularly, to an apparatus obtained by improving an conventional syringe formed with an injection flow passage including an injection needle, so as to share a portion of the injection flow passage except the injection needle or to form a suction flow passage completely independent of the injection flow passage, thereby further smoothing suction of a liquid medicine. The syringe includes an injection needle (10) and a cylinder (20) and formed with an injection flow passage extending from the cylinder (20) to the injection needle (10), and further includes an opening/closing means (400) for selectively opening or closing the injection flow passage； a suction flow passage formed from a pointed hollow cap (10) to the cylinder (20) and provided with a through-hole (200) formed in any one of the injection needle (10), a connector for connecting the injection needle (10) to the cylinder (20), and the cylinder (20) to establish communication between an inside and an outside thereof； and a valve means (300) for intermittently controlling opening or closing of the suction flow passage by a user's manipulation. The syringe is configured such that the separate suction flow passage bypassing the injection needle is formed in a conventional syringe to more smoothly perform suction of the liquid medicine, thereby maximizing user's convenience and marketability of the product, and further configured to forcibly close the suction flow passage upon injection of the liquid medicine.
