The aim of the concept of perimeter control is to manage the transfer flow between urban road networks. However, there is a lack of description on the behavior of transfer flow between networks in relation to the macroscopic fundamental diagram (MFD). Hence, this paper suggests a description of transfer flow and investigates it with microscopic simulation experiments. The results found that the network outbound demand strongly influences the outflow regardless of spatial inhomogeneity. Another finding is that the boundary capacity influences the network outflow. The effect of restriction on outflow of a network due to limited supply level of a neighboring network was also checked. Furthermore, it was found that a network’s inflow and outflow in each direction (north, south, east, and west) is proportional to the demand ratio. Finally, the suggested description of transfer flow has been confirmed, and this can be useful for various analyses on inter-network traffic dynamics.