PURPOSE: To automatically obtain an absolute degree of accuracy by providing a dead-time compensation means for compensating the start timing of a running material cutter in accordance with a deviation between an actual crop length and a desired crop length and a transfer speed.

CONSTITUTION: With the use of a transfer distance measuring unit 4 for measuring a feed distance of a material to be cut (material to be rolled) running on a transfer device and two material detectors 6, 7 arranged at the front and rear ends of a running machine 3, an actual crop length is calculated to accordance with a feed distance during the period from the time when the front end of the material 2 to be cut passes over the inlet side material detector 6 to the time when the front end of the material 2 passes over the outlet detector 7 after the front end part of the material is cut by a shear 3, and a difference in distance between the input and outlet detectors 6, 7. Then, in accordance with a deviation between thus calculated crop length and a set desired crop length, a control device 8 compensates the dead time upon start of shearing. With this arrangement, the dead time upon start of shearing is automatically compensated to enhance the yield.