IN-VEHICLE NETWORK SYSTEM

An in-vehicle network system includes: an upper device (10); a first intermediate unit (21; 23) that is connected to the upper device directly or via at least one device and is configured to communicate with the upper device using a first communication system; a second intermediate unit (22; 24) that is connected to the upper device directly or via at least one device and is configured to communicate with the upper device using a second communication system; and a lower unit (31; 32, 33) that is connected to the first intermediate unit and the second intermediate unit and is configured to communicate with the first intermediate unit using the first communication system and communicate with the second intermediate unit using the second communication system.