A bed height adjustment system for adjusting height of a bed of a vehicle includes: an air spring supporting the bed; a valve unit connected to an air tank and configured to adjust height of the air spring by supplying and discharging air; a relay provided with a dump-signal line and a return-signal line each connected to the valve unit; a pressure switch configured to be switched between an ON state and an OFF state based on whether air is supplied from the valve unit; and an indicator that becomes illuminated state when powered when the pressure switch is in the ON state and becomes non-illuminated state when the pressure switch is in the OFF state.