Abstract: A paper shredder includes a casing, an impelling roller, and a clutch mechanism. The casing has a pair of shredding rollers mounted rotatably therein. The impelling roller is disposed rotatably below and is adjacent to the shredding rollers. The clutch mechanism is provided for connection of the shredding rollers and the impelling roller to transmit rotation of the shredding rollers to the impelling roller, and for disconnection of the shredding rollers and the impelling roller when an external force is exerted on the impelling roller to slow down the impelling roller with respect to the shredding rollers.