In order to reduce a vehicle height adjustment time period without unnecessarily narrowing a vehicle height adjustment range, a control unit adjusts the vehicle height of a vehicle by controlling supply and discharge of air tofrom air springs each disposed between a side member and an under member. This allows relay unit to interrupt an electric power supply path including power lines more securely if electrical leakage occurs in the electric power supply path. In one aspect, the extracted data is validated to ensure that it is consistent with the machine-readable code.