We developed a system that extracts and visualizes the network structures from relational data on spreadsheets. Visualization through network diagrams obtained from relational data is indispensable to understanding their structure. However, time-consuming tasks are involved in visualizing these networks. The purpose of this research was to support the extraction and visualization of network structures from relational data. We developed an interface that coordinates spreadsheets with visualization tools. It simplifies the visualization of networks from relational data and enables their structures to be easily understood.