This first mixing and injecting tool is for allowing a first medicine container storing a medicine to be dissolved to communicate with a second medicine container storing a dissolving medicine, and for moving the medicine to be dissolved from the first medicine container to the second medicine container. The mixing/injecting tool comprises: a cylindrical body that includes openings on a first end and a second end in an axial direction, the second end being attachable to a medicine inlet section of the second medicine container； a receiving member that is arranged on a first end side of an interior of the body, is configured so as to receive a medicine discharge section of the first medicine container, and is movable in the axial direction between at least a first position and a second position inside the body； and a needle unit that is arranged more to the second end side than the receiving member inside the body, includes a first needle part capable of puncturing a medicine discharge section of the first medicine container and a second needle part that communicates with the first needle part and is capable of puncturing the medicine inlet section of the second medicine container, and is movable in the axial direction between at least a third position and a fourth position inside the body. The needle unit is configured so as to be locked to the body at the third position. The receiving member is configured to release the fixing of the needle unit when receiving member has received the first medicine container at the first position and has moved to the second position together with the first medicine container. The first needle part is configured to puncture the first medicine container while the first medicine container is moved with the receiving member from the first position to the second position. The second needle part is configured to puncture the second medicine container while the needle unit moves from the third position to the fourth position.L'invention c
