To eliminate a large motor for revolving a cutter for forming a finished product and improve the working efficiency thereof.

In a working method for a corrugated board sheet, a single-faced corrugated board sheet 1 formed into an endless shape is cut into a plurality of fine width belt-shaped core materials 3 simultaneously by a cutter 2, and paste is applied on a top on the lower end of a corrugated board 1a in the state that the corrugation direction of the corrugated sheet 1a bonded on the lower side of a liner 1b is almost horizontal and positioned on the same plane by a pasting means, and then a plurality of core materials 3 are bonded one another by the paste applied on the top of the lower end of the corrugated board sheet la by twisting the corrugation direction of the corrugated board sheet 1a so that the corrugations are faced in the vertical direction. The corrugated materials 3 are cut in the length direction at proper intervals to form cores.