Abstract: For connecting an air compressor to a pneumatic tool, a revolvable quick coupling comprising a first air pipe connector revolvably secured to an intermediate connecting member by a ball bearing means and connected to an air output pipe of an air compressor, a second air pipe connector secured to said intermediate connecting member by a front socket, a retainer, an inner socket, a seal ring, a stepped metal element and a spring means for connecting to an air input pipe of a pneumatic tool. Pressing on the retainer causes the second air pipe connector to disconnect from the front socket and simultaneously causes said seal ring to seal the air passage inside the coupling. Rotating the pneumatic tool causes the second air pipe connector to rotate on the first air pipe connector without twisting the air output pipe of the air compressor.