The present invention relates to a syringe, and more particularly, to an apparatus obtained by improving a 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 is configured such that the separate suction flow passage bypassing the injection needle is formed in the conventional syringe to more smoothly perform suction of the liquid medicine, thereby maximizing user's convenience and marketability of the conventional syringe, and further configured to forcibly close the suction flow passage upon injection of the liquid medicine.