An object is to provide a communicating needle of simple construction which is attached to a medical infusion bag to connect two or more containers in fluid communication with each other. The communicating needle for connecting two or more containers to communicate includes a tip having an outlet opening formed thereon and a seal member integrally formed with the communicating needle to seal the outlet opening. The seal member readily comes off the communicating needle when acted upon by an external force, causing the outlet opening to open. The communicating needle may be covered by a seal body.