Nebulizers are inhalers for the treatment of the respiratory troubles through converting liquid medicines into aerosols of the respirable size(1~5㎛) in the lower respiratory tract. In this study, to find the cause of performance degradation of baffle type pneumatic nebulizer, reverse engineering was firstly conducted. And it is concluded that deformation of orifice shape after injection molding is a major cause. So, to reduce the deformation after injection molding, the injection molding analysis was fulfilled and the improved model which has the reduced deformation of 50.0% was suggested. Finally, to improve the spraying atomization performance, CFD analysis was conducted. And through the design modification of the orifice parameters, the baffle type pneumatic nebulizer model, which has the higher suction velocity of 7.0% and the higher mass flow rate of 100%, was developed.