Abstract: A grinding device for grinding a cylinder that has a rotating shaft includes an immovable component, a movable component, and a grinding component. The immovable component has a positioning unit. The cylinder has the rotating shaft positioned by the positioning unit. The movable component has a carrying portion and is such installed on the immovable component that the movable component can move axially along the rotating shaft. The carrying portion positionally corresponds to the cylinder. The grinding component is located on the carrying portion and positionally corresponds to a surface of the rotating shaft. The grinding device thereby is able to grind the rotating shaft of the cylinder evenly with reduced labor costs.