A drug solution transferring device that can suppress dispersion of a toxic drug solution to a surrounding environment is provided. The drug solution transferring device includes a barrel (1) provided with an opening (10), and a connection tool (2) for connection to the barrel (1). The barrel (1) includes an elastic member (121) for closing the opening (10). The elastic member (121) is formed of a plurality of membranes (121 a, 121 b) overlaid together. The membrane (121 a, 121 b) has a projection (123) projecting into the barrel (1). The connection tool (2) includes a first needle (231) having a sharp tip end (231 a). The first needle (231) has a liquid hole (234) extending in an extending direction of the first needle (231). When the needle (231) penetrates through the projection (123) of the membrane (121a, 121b), an inside and an outside of the barrel (1) are in communication with each other through the liquid hole (234) to allow transference of the drug solution between the barrel (1) and the connection tool (2).
