Abstract: This disclosure relates to improvements in a slitter device which cuts a roll-shaped long piece rotatably supported almost horizontally by a guide holder rod into round slices with the predetermined width using a rotary cutting blade which moves back and forth perpendicular to the long piece, and more particularly to the safety control of the slitter device which immediately stops the rotation of the cutting blade or retracts the cutting blade from the guide holder rod or uses other methods when the rotary cutting blade contacts the guide holder rod.