PURPOSE: To improve efficiency by forming a traveling-speed synchronization mechanism from a storke leading-out means which drives by leading-out a part of the first stroke of a cutting blade, thus reducing the dimension of the mechanism and permitting the cut of the high-speed traveling material.

CONSTITUTION: When a material which travels penetrating through chucks 33,33' a dolly 16 is driven to increase its speed in synchronization with the traveling speed of the material, and then a traveling-speed synchronization signal is generated to drive the hydraulic cylinder 32 of a material cutting mechanism 18, and a cutting blade 30 lowers, and aprt of the first lowering stroke is introduced into a speed synchronization mechanism 20 by a stroke leading means 34, and the chucks 33, 33' catch the material. At the same time, a clutch 24 is cut-off, and the dolly 16 travels in synchronization with the material, pulled by the material, and the relative speed difference between the material cutting mechanism 18 and the material becomes zero, and the material is cut with the continuous lowering stroke of a blade 32. Thus, the dimension of the cutter can be reduced, since the speed synchronization mechanism does not necessitate a chuck driving means.