An inflation bulb (200), suitable for use with a sphygmomanometer, is internally hollow, and comprises a gas inlet end (210) and a gas outlet end (220). An inner side of the gas inlet end (210) forms inwardly protruding lips (212) that are approximately flat. The lips (212) define a gas inlet opening (213) through which exterior air gas is allowed to penetrate the inflation bulb (200). The gas outlet end (220) includes a gas outlet opening (222). The gas outlet opening (222) is further connected to a gas intake pipe (210). When the inflation bulb (200) is pressed, the lips (212) occlude the gas inlet opening (210), which compels an inner air gas to exit via the gas outlet opening (222). Once the pressing action is released, the inflation bulb (200) recovers its initial state and causes the lips (212) to open the gas inlet opening (213). By repeatedly pressing and releasing the inflation bulb (200), a cuff of the sphygmomanometer is inflated.