Regulators are key components for controlling the pressure of compressed air supplied to LCD and semiconductor production lines. The regulator consists of a solenoid valve, a diaphragm, and a poppet valve. Among them, the shape of the diaphragm is known to influence the control performance and durability of the regulator. However, studies related to diaphragms are lacking. Therefore, in this paper, three types of diaphragms with different shapes are mounted on the regulator, and the control performance characteristics are confirmed and the results are presented.