Abstract: The present invention relates to a slitter apparatus with a compensating device for slitter blades thereof to provide a stable or proper operation for cutting a corrugated cardboard sheet. The slitter apparatus according to the present invention is comprised of a plurality of slitter heads 20-24 disposed in-line in the width direction of the corrugated cardboard sheet, each of the slitter heads including a disk-shaped slitter blade 40 for cutting the corrugated cardboard sheet being continuously fed along a feeding line by moving the disk-shaped slitter blades toward the corrugated cardboard sheet. The apparatus further comprises positioning sensors 50 for detecting the vertical position of each of the disk-shaped slitter blades 40, and an optical sensor 58 having an optical axis 60 generally disposed in a parallel relationship with respect to the corrugated cardboard sheet.