Abstract: A regulator for pneumatic system comprising a connecting bracket for connecting other air conditioning units to a regulator body. Because of this connecting bracket, the air conditioning units to be connected to each other can be modularized. The connecting bracket has, at its both ends, a pair of projection-like pawl sections which are engageable respectively with engaging sections formed respectively on outer peripheral surfaces of the other air conditioning units. Incorporated in the connecting bracket is a pressure gage for detecting secondary pneumatic pressure within the regulator body. The pressure gage comprises a pressure detecting section, a pressure display section, pressure setting section and an abnormality alarm section.