IN-VEHICLE SYSTEM

An in-vehicle system installed in a vehicle including a plurality of relay devices, wherein the plurality of relay devices are installed in a plurality of installation areas partitioned in the vehicle and include a plurality of connectors corresponding in number to the plurality of installation areas, the number and shapes of the plurality of connectors are standardized between the plurality of relay devices, harnesses extended from the plurality of installation areas are connected to the plurality of connectors either directly or via relay connectors, the plurality of relay devices include: a first relay device in which harnesses extended from different installation areas are connected to the plurality of connectors; and a second relay device other than the first relay device, and the number of relay connectors connected to the first relay device is no greater than the number of relay connectors connected to the second relay device.