The present invention relates to an external cap for liquid medicine injection device and, more specifically, an apparatus in which an outer cap (100) configured to temporarily form a suction flow passage only by suction of the liquid medicament, and to be removed to open a liquid medicine injection flow passageway, the liquid medicine injection device (200) being improved by including a filter (240) for filtering foreign substances contained in the liquid medicine, establishing a tight seal between the inner peripheral surface of the outer cap (100) and the peripheral surface of the liquid medicament injection device (200) so as to reliably create negative pressure in the injection flow passage and prevent the medicament from liquid enters the injection needle (210) during suction of the liquid medicine. the outer cap (100) of the liquid medicament injection device (200) according to the present invention includes a suction needle (110) for sucking the liquid medicament and a cap hub (120) hermetically coupled to the liquid medicament injection device liquid medicine (200), and the outer cap (100) comprises an inner space extending from the suction needle (110) to the cap hub (120), the inner space being formed with an injection needle receiving section (130) for receiving the injection needle (210) when the liquid medicine injection device (200) is mounted, and where a sealing means configured to contact the peripheral surface of the liquid medicine injection device (200), whose function is to maintain tightness between the inner space and the receiving section of the injection needle (130) when the liquid medicine injection device (200) is mounted, is disposed at the inlet of the injection needle receiving section (130).a presente invenção se refere a uma tampa externa de dispositivo para injeção de medicamento líquido e, mais especificamente, a um aparelho no qual uma tampa externa (100) configurada para formar temporariamente uma passagem
