An information processing system is provided with a center server, a first moving object that communicates with the center server, and a second moving object that communicates with the center server. The first moving object is provided with: a posted information acquisition unit that acquires posted information pertaining to travel guidance; and a posted information sending unit that sends posted information to the center server. The center server is provided with a guidance information storage unit that stores guidance information based on posted information. The second moving object is provided with a travel guidance execution unit that executes travel guidance for the second moving object, said travel guidance being for a travel route to a set destination. The travel guidance execution unit uses the guidance information in the guidance information storage unit to execute travel guidance.