Development of Automatic Network Replication System for OpenFlow Network In this study, we developed an automatic network replication system for Open Flow network. This system can automatically and virtually replicate Open Flow network according to captured information. This system consists of mainly two functions: Message Capture Function (MCF), Network Emulation Function (NEF). MCF is located between Open Flow controller and Open Flow switch. MCF can capture message information that is exchanged between Open Flow controller and Open Flow switch. In addition by use of LLDP, MCF can detect link information between Open Flow switches. Then, MCF performs topology inference by link information. NEF can replicate Open Flow network according to captured message information and link information. Users can do a test newly developed function of Open Flow freely and easily on just one PC by use of this system.