A filtering syringe comprising an injection needle , a cylinder and a plunger , the filtering syringe further comprising: a suction flow passage formed from a pointed hollow cap to the cylinder and provided with a one-way valve means ; and an injection flow passage formed from the cylinder to the injection needle and provided with a detachable opening/closing means for selectively opening and closing the injection needle and a filter means for filtering out foreign substances from a liquid medicine, wherein the injection flow passage and the suction flow passage share portions of the flow passages or the injection flow passage is formed independently of the suction flow passage, whereby a flow passage portion from the filter means to the injection needle in the injection flow passage is formed independently of the suction flow passage, characterized in the detachable opening/closing means accommodates the injection needle , wherein the one-way valve is opened and closed by one of: a) automatically depending on a direction of pressure on the liquid medicine; b) in response to a rotation manipulation of the cylinder ; or c) simply whether the cap is separated, the filtering syringe comprising an injection needle is further characterized in a hermetic space formed at a lower portion of the opening/closing means and surrounds a hub of the injection needle to maintain airtightness, and wherein an adhesive material for securing a needle body and the hub of the injection needle to each other is accommodated in the hermetic space of the opening/closing means so that the adhesive material is isolated from the liquid medicine, and wherein the opening/closing means is fixedly installed with the cap so that the opening/closing means is separated together with the cap in response to separation of the cap . a suction flow passage formed from a pointed hollow cap to the cylinder and provided with a one-way valve means ; and an injection flow passage formed from the cylinder to the injection needle and provided with a detachable opening/closing means for selectively opening and closing the injection needle and a filter means for filtering out foreign substances from a liquid medicine, wherein the injection flow passage and the suction flow passage share portions of the flow passages or the injection flow passage is formed independently of the suction flow passage, whereby a flow passage portion from the filter means to the injection needle in the injection flow passage is formed independently of the suction flow passage, characterized in the detachable opening/closing means accommodates the injection needle , wherein the one-way valve is opened and closed by one of: a) automatically depending on a direction of pressure on the liquid medicine; b) in response to a rotation manipulation of the cylinder ; or c) simply whether the cap is separated, the filtering syringe comprising an injection needle is further characterized in a hermetic space formed at a lower portion of the opening/closing means and surrounds a hub of the injection needle to maintain airtightness, and wherein a) automatically depending on a direction of pressure on the liquid medicine; b) in response to a rotation manipulation of the cylinder ; or c) simply whether the cap is separated, <EOS>