A non-permeable pipe connector structure, the design of which effectively prevents external material (such as vapor and miscellaneous substances, etc.) intrusion. To obstruct the intrusion of external matter into the pipe connector, a ball bearing holder is disposed at the pipe connector, enabling even greater ball bearing durability and, furthermore, free rotation. A protective flange is disposed as the bottom surface of the ball bearing holder such that when the coupling nipple and the connector base are fastened together, the protective flange effectively blocks external matter, thereby precluding entry to avert subsequent damage to the bearings. Furthermore, a rubber sealing ring sleeved onto the annular groove prevents vaporous or acid and alkaline substance intrusion into the bearings, and has safe defensive effectiveness.