A coinfusion apparatus that automatically performs a part or the entirety of a coinfusion processing and that can prevent a transfusion bag from being exposed to radiation is provided. The coinfusion apparatus 1 includes: a coinfusion operation section 2 a coinfusion processing room 204 a supply section 100 and a transfusion bag retention section 4. The coinfusion operation section 2 consists of the first robot arm 21 and the second robot arm 22. The first robot arm 21 retains the medical agent container 10. The second robot arm 22 performs an operation to insert the syringe needle of the syringe 11 to the mouth section of the medical agent container 10 retained by the first robot arm 21 and an operation to insert the syringe needle of the syringe 11 to the coinfusion mouth of the transfusion bag 12. The coinfusion processing room 204 holds the coinfusion operation section 2. The supply section 100 supplies the medical agent container 10 and the syringe 11 into the coinfusion processing room 204. The transfusion bag retention section 4 retains the transfusion bag 12 at the outer side of the coinfusion processing room 204 and positions the coinfusion mouth of the transfusion bag 12 at the coinfusion communication mouth 202b formed in the coinfusion processing room 204.
