[Problem] To always perform accurate pressure feedback control, and control the discharge flow rate of liquid chemical with high precision, even in situations in which the pressure setting value of the operation pressure differs due to changes in the type of liquid chemical, etc. [Means of solution] A pump 11 has a pump chamber 13 and an operation chamber 14 separated by a diaphragm 12 comprised of a flexible membrane, and performs the intake and discharge of liquid chemical in accordance with the change in pressure inside the operation chamber 14. An electro-pneumatic regulator 32 supplies operation air to the operation chamber 14. In addition, in the present system, a plurality of pressure sensors 51, 63 having different pressure detection ranges is provided as pressure detection means for detecting the operation air pressure. A controller 40 selectively employs any of the detection results of the plurality of sensors 51, 63 in accordance with the pressure setting value of the operation air that is set for each use, and performs pressure feedback control.