Information providing system and server

An information providing system includes: a plurality of vehicles each configured to perform inter-vehicle charging; and a server. Each of the plurality of vehicles is configured to transmit unattended power-supplying permission information to the server when the user performs an operation of permitting unattended power supplying. In the matching process, the server is configured to permit to set, as a power-supplying vehicle, a vehicle having transmitted the unattended power-supplying permission information. The server is configured to notify, to the unattended power-supplying vehicle matched through the matching process, a confirmed matching content including information of the power-receiving vehicle. The unattended power-supplying vehicle having received this notification is configured to unlock a lid, which covers a power-supplying connector of the unattended power-supplying vehicle, and permit the unattended power supplying in response to the matched power-receiving vehicle being parked in proximity of the unattended power-supplying vehicle.