A pressure regulating device used for an aerostat bag body comprises a pedestal, a bracket, a drive mechanism, a performing mechanism, a valve cover, and a cam, wherein the bracket is arranged on thesurface of one side of the pedestal, and is positioned on the edge of the opening of the pedestal; the drive mechanism is connected with the bracket, and comprises a first rotary shaft; the performingmechanism is provided with a first end and a second end which are opposite to each other, and comprises a second rotary shaft parallel to the first rotary shaft; the first end is in pivotal connection with the bracket through the second rotary shaft, and is fixedly arranged on the edge of the opening through the bracket; the valve cover is matched with the opening, and the second end of the performing mechanism is connected with the valve cover; the cam is provided with a pivotal part and a resisting part which are oppositely arranged; the cam is connected with the first rotary shaft throughthe pivotal part; the cam rotates relative to the bracket along with rotation of the first rotary shaft; when the cam rotates to the state that the resisting part resists against the performing mechanism, the valve cover and the pedestal are separated to form an opening position; and when the cam rotates to the state that the resisting part is separated from the performing mechanism, the valve cover and the pedestal are closed to form a closing position. The invention further provides an aerostat. The pressure regulating device and the aerostat can automatically and manually regulate pressureaccording to an environment condition.