A one-piece gas pressure regulator, comprising a main body having a first threaded port at the bottom thereof for a threaded connection with a high-pressure gas bottle. An admission passage is formed above the first threaded port and extended to a hollow pressure chamber within the main body. The hollow pressure chamber has an escape channel for ejecting the gas via an output control element, wherein the main body includes a second threaded port having a greater diameter and is positioned above the hollow pressure chamber. The second threaded port is adapted to receive a cylindrical body. The inside of the cylindrical body is divided by a partition into an upper and a lower chamber. The partition has a through hole in the middle thereof. The upper chamber is adapted to receive a pressure detector while the lower chamber is used to receive a pressure-adjusting element. The through hole is formed in such a way that a connecting head of a pressure detector is extended into the through hole. In this way, the main body and the cylindrical body are integrated into a body, and the upper portion of the cylindrical body and the pressure detector are formed in a one-piece pressure gauge while the lower portion thereof serves as an automatic gas-pressure balancing/regulating chamber for the lifting action of the pressure-adjusting element. As a result, the gas pressure regulator in accordance with the invention achieves an overall sense. Meanwhile, the pressure gauge can be protected from skewing impacts that cause damage.