Abstract: There are provided a pressure sensor sensing or measuring air pressure and a device for preventing air inflow, which is used to prevent air, moisture and foreign substances from flowing into the pressure sensor. The pressure sensor includes an air flow part through which air to be measured, the pressure of which is to be measured, flows, a pressure sensing part sensing the pressure of the air to be measured, which flows through the air flow part, and an air blocking part installed between the air flow part and the pressure sensing part, preventing the air to be measured from flowing into the pressure sensing part, and causing, at least, a movement or a deformation according to a pressure change of the air to be measured. The pressure sensor completely prevents moisture or foreign substances from flowing into the pressure sensor, thereby minimizing defects of the pressure sensor.