Abstract: A device for dissolving and delivering a drug in a transfusion liquid includes a transfusion liquid container, a drip chamber, a transfusion tube communicating with the drip chamber, and a cylindrical body having first and second end portions. The cylindrical body is communicable with the container at the first end portion, and with the drip chamber at the second end portion. A first hollow needle communicates with, and projects outwardly from, the cylindrical body. The first needle establishies communication between the container and a drug container containing a drug to be introduced into the transfusion liquid, through the cylindrical body, by piercing into the drug container. A drug container is accommodated in an accommodating member provided on the cylindrical body. A movable valve body is provided inside the cylindrical body at an initial position at which its side portion does not clog the first needle.