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 provided with an opening, and a connection tool for connection to the barrel. The barrel includes an elastic member for closing the opening. The elastic member is formed of a plurality of membranes overlaid together. The membrane has a projection projecting into the barrel. The connection tool includes a first needle having a sharp tip end. The first needle has a liquid hole extending in an extending direction of the first needle. When the needle penetrates through the projection of the membrane, an inside and an outside of the barrel are in communication with each other through the liquid hole to allow transference of the drug solution between the barrel and the connection tool.
