In this paper, we derive the average message delivery delay in a geographic DTN routing with multiple mobile agents, where mobility patterns are given by random walk on a graph and message routing algorithm is the Random algorithm. A geographic DTN routing aims at realization of message delivery among multiple (generally, geographically-dispersed) geographic locations on a field without necessity of specific communication infrastructure by utilizing mobility of mobile agents. We model the behaviors of mobile agents as multiple random walks on a graph. Our analysis reveals the effect of system parameters -- the number M of mobile agents on the field and the number K of message loads at a geographic location -- on the average message delivery delay.