To provide a safety device for shredder which prevents an injury of fingers by a cutter for shredding of a shredder.

The safety device for a shredder is characterized by providing a guiding passageway 9 of the material to be shredded 7 in the device body 5 which penetrates the device body up and down and having a mechanism so that a finger does not reach the cutter 13 for shredding in the shredder 3 when the finger 11 is inserted into the guiding passageway from the entrance 9a of the guiding passageway. The device body has a height that does not reach the cutter for shredding in the shredder when the finger is inserted into the guiding passageway from the entrance of the guiding passageway wherein the guiding passageway is getting narrower towards the lower part. The shredder is characterized by fitting the safety device for the shredder so that the guiding passageway communicates with the insertion port 15 of the material to be shredded.