A modular external infusion device that controls the rate a fluid is infused into an individual’s body, which includes a first module and a second module. Keying means is provided between the base plate and the recessed area so as to prevent the base plate from mismating with the socket base. The EKB has a constitution in which a device as a leaf of the tree holds a leaf key and a limited node key, and a specific enabling key block is generated and distributed to a group specified by a specific node to limit devices that can be renewed. In addition, a high voltage line 40 attached to the bracket 60 also deforms following the deformation of the bracket 60.