A wireless ad hoc communication system is provided in which in the case where an alternative route can not be discovered in a certain node, a restoration is attempted in an intermediate node instead of deleting all routes up to a transmission source.In order to do so, a route discovery process 20 discovers and sets a route when a corresponding route is not set at the time of data communication request 10. A link state management process 40 monitors a state of a link 30 on the route set by the route discovery process 20, and updates a link state in a route table of each wireless terminal. When the link quality deteriorates, a route information notification process 50 notifies the link state to urge a retention of transmission data. An alternative route search process 60 searches an alternative route when the link quality deteriorates, and traces back to a terminal on the transmission side in order to search further when the alternative route is not discovered. A route switching process 70 switches a possible alternative route as a qualified route.