The topic of getting information from sensor networks is becoming more important. Middleware will be required to manage various sensor data in future. We propose the Semantic Sensor Network (SS), which applies an ontology to sensor data and enables such data to be treated more easily. However, users have great difficulty to understand the information on the SS because its semantic data are complicatedly related with each other and the data and their relations evolve in time. The requirements for visualizing such information are; 1) the SS must give users the information appropriately, and 2) the SS must answer the users' queries. To meet these requirements, we propose Viewlon, software for visualizing information on the SS. To give the information appropriately, information display levels and a timeline view are introduced. In addition the functionality of processing queries provides the required information to users interactively. We experimented with Viewlon in a simulation environment, and the results show that Viewlon has the ability to present information to users and to answer their queries correctly.