PURPOSE: To deburr a slab cut through welding easily and reliably by constructing such that the lower cutter will move gradually while point contacting with the burr.

CONSTITUTION: In deburring device to be arranged in welding line for cutting a continuously casted material into slabs of predetermined length, the upper cutter 12 in upper cutter mechanism 1 is normally at the lift position hihger than the bus line level of roller table R while lowered to said level when deburring. The lower cutter 35 is fixed while inclining in lateral direction of slab. A differential transfer is fixed between horizontally movable table 32 and lower cutter holder 34 to detect relative moving distance. The lower cutter mechanism 3 is normally at the lowering position lower than said level and lifts to said level when deburring then moves horizontally. Consequently, it is deburred easily.