A medical device for forming a liquid communication path, comprising: joining members (1, 3) for forming the communication flow path between objects to be communicated with each other； and a protective cap (2) having a tubular shape with a closed end, holding a germicide-impregnated member (18) at the deepest end of the protective cap, and capable of being mounted to at least one of the joining members which are being separated from each other. The inner peripheral surface of the protective cap forms a space (19) for surrounding the tip of the joining member, and the dimensional relationship between the joining member and the protective cap is set so that the germicide-impregnated member (18) faces the tip of the joining member with a spacing between the members. A sealing member (8) is mounted to the inner peripheral surface of the opening end of the protective cap or to the outer peripheral surface of that portion of the joining member which corresponds to the opening end of the protective cap, and when the protective cap is in a mounted state, the sealing member is pressed between the outer peripheral surface of the joining member and the inner peripheral surface of the protective cap to form an airtight structure for the space. The mounting of the cap on the joining member effectively sterilizes the tip of the joining member and, in addition, avoids leakage of the germicide due to the contact of the joining member with the germicide-impregnated member.Un dispositivo médico para formar una trayectoria de comunicación de líquido incluye miembros 1, 3 de conexión que forman una trayectoria de comunicación de flujo entre objetos a ser comunicados cuando se unen y una tapa protectora 2 que tiene una forma cilíndrica con un extremo cerrado sujeta un miembro 18 impregnado con germicida en el fondo y puede unirse a por lo menos uno de los miembros de conexión cuando se separan. Se determina una relación dimensional entre el por lo menos uno de los miembros de conexión y
