[Problem] To provide a coinjection device with which it is possible to limit the omission of preparatory work required aside from a coinjection process performed using a coinjection device. [Solution] The coinjection device executes a coinjection process in which medicine is sucked from a medicine container using a syringe, on the basis of preparation data, and the medicine is injected from the syringe into an infusion container. Aside from the coinjection process, if preparatory work must be carried out before executing the coinjection process (S3: Yes), a pre-determined message relating to the preparatory work, for example, can be communicated (S4, S6).
