A rotating cylinder includes a cylinder body, a piston, a piston shaft assembly, a main body and a guiding assembly. The cylinder body defines a receiving chamber. The piston, the piston shaft assembly, the main body and the guiding assembly are received in the receiving chamber. The piston shaft assembly is fixed to the piston, and defines at least one guiding groove lengthwise thereof. Each guiding groove includes a spiral portion and an extending portion. The main shaft is non-rotatably connected to the piston shaft assembly away from the piston and exposed out of the cylinder body. The guiding assembly sleeves on the piston shaft assembly and is slidably connected with the at least one guiding groove. The main shaft is driven to rotate when the guiding assembly engages the spiral portion, and move lengthwise when the guiding assembly is slidably connected with the extending portion.