A vehicle-height adjustment system, comprising: a vehicle-height adjustment actuator provided so as to be associated with a wheel; and a pressure-medium supply and discharge device configured to supply and discharge a pressure medium to and from the vehicle-height adjustment actuator, wherein the pressure-medium supply and discharge device comprises a tank configured to store the pressure medium, characterized in that the vehicle-height adjustment system comprises a tank-pressure controller (80, 90, 92, 94) configured to control a tank pressure based on a vehicle height for the wheel and an inside temperature (Ti), wherein the tank pressure is a pressure of the pressure medium stored in the tank, and the inside temperature (Ti) is a temperature in the vehicle-height adjustment system, wherein the pressure-medium supply and discharge device comprises a pressure-medium supplier (30, 44, 63) configured to supply the pressure medium to the tank, wherein the tank-pressure controller (80, 90, 92, 94) comprises a supply controller (80, 90, 92, 94) configured to control the pressure-medium supplier (30, 44, 63) to supply the pressure medium to the tank when the tank pressure is less than a supply start threshold value, wherein a temperature difference (ΔT) is a value obtained by subtracting, from the inside temperature (Ti), an outside-air temperature (To) that is a temperature of outside air, and wherein the supply controller (80, 90, 92, 94) comprises a first temperature-difference-dependent changer (80, 90, 92, 94) configured to set the supply start threshold value (Pil) in a case where the temperature difference (ΔT) is large to a value greater than the supply start threshold value in a case where the temperature difference (ΔT) is small. a vehicle-height adjustment actuator provided so as to be associated with a wheel; and a pressure-medium supply and discharge device configured to supply and discharge a pressure medium to and from the vehicle-height adjustment actuator, wherein the pressure-medium supply and discharge device comprises a tank configured to store the pressure medium, characterized in that the vehicle-height adjustment system comprises a tank-pressure controller (80, 90, 92, 94) configured to control a tank pressure based on a vehicle height for the wheel and an inside temperature (Ti), wherein the tank pressure is a pressure of the pressure medium stored in the tank, and the inside temperature (Ti) is a temperature in the vehicle-height adjustment system, wherein the pressure-medium supply and discharge device comprises a pressure-medium supplier (30, 44, 63) configured to supply the pressure medium to the tank, wherein the tank-pressure controller (80, 90, 92, 94) comprises a supply controller (80, 90, 92, 94) configured to control the pressure-medium supplier (30, 44, 63) to supply the pressure medium to the tank when the tank pressure is less than a supply start threshold value, wherein a temperature difference (ΔT) is a value obtained by subtracting, from the inside temperature (Ti), an outside-air temperature (To) that is a temperature of outside air, and wherein the supply controller (80, 90, 92, 94) comprises a first temperature-difference-dependent changer (80, 90, 92, 94) configured to set the supply start threshold value (Pil) in a case where the temperature difference (ΔT) is large to a value greater than the supply start threshold value in a case where the temperature difference (ΔT) is small.