PROBLEM TO BE SOLVED: To provide a cylinder washing apparatus which does not press a detecting roller for detecting a diameter of a washing cloth during winding the washing cloth.SOLUTION: A detecting roller 87 is connected with a supporting shaft 85 provided on a plate 3 through an L-shaped arm 86, and a rod 89 is provided on a stopper 88 on the other side. A diameter detecting lever 84 for detecting the diameter of the washing cloth wound on a washing cloth winding roll 12 is provided. An reverse rotation preventing means 90 is provided, and one side is fixed on a washing cloth winding roll shaft 12, and the other side is fixed on a winding plate 91 on which one end is brought into contact with the rod 89, and the winding lever 94 is provided at the other end. When the washing cloth is wound by the plate 3 moved by an air cylinder 5, the winding lever 94 is brought into contact with the frame 4 to separate the rod 89 from the winding plate 91, and an energizing means 92 of the winding plate 91 separates the detecting roller 87 which is brought into contact with the surface of the washing cloth winding roll 12 from the surface of the washing cloth during winding through an opened rod 89 and the L-shaped arm 86.