A drug mixing device is disclosed. The drug mixing device comprises a first container for holding a first component of a drug to be mixed, a second container for holding a second component of the drug to be mixed, fluidly coupled to the first container； and a fluid driver fluidly coupled to the first container and configured to drive a driving fluid into the first container. The mixing device is arranged such that, in use, when the fluid driver drives the driving fluid into the first container, at least some of the first component of the drug to be mixed flows to the second container.
