To decrease the pressure control defects of the compressed air for roll reduction occurring in the dust in compressed air, to cause rolls to be screwed down under adequate rolling force, to enhance the reliability of the operation of a pressure controller, eventually to improve the yield of products and to provide the pressure controller of the compressed air for roll reduction capable of prolonging the life of the rolls.

The pressure controller of the compressed air to be used with a roll screw-down device to execute the rolling reduction of the rolls for holding a steel strip or steel sheet during passage is equipped with a pressure measuring instrument 14 for measuring a change in the compressed air pressure within a roll screw-down cylinder, a selector valve 15 for supply for the purpose of raising the compressed air pressure in the screw-down cylinder in accordance with the measurement and a selector valve 16 for discharge for lowering the compressed air pressure in the screw-down cylinder by discharging the compressed air in the screw-down cylinder in accordance with the measurement.