To make a fold at a rule line with good accuracy by reinforcing the rule line formed in the drawing process for the purpose of not generating the deviation of sticking in the rule line folding and pasting process for forming a corrugated box when the corrugated box is manufactured.

In the rule line folding and pasting process for forming a corrugated box, rule lines to be formed in a drawing process using a corrugated board product forming machine are reinforced by a folding rule line reinforcing member 1 for the purpose of not generating the deviation of sticking in the pasting process so that the rule lines can be folded neatly. In that case, the member is constituted of a plane plate-shaped main body 4, a straight line- shaped rule line forming protrusion 2 formed on one face of the main body 4 and reinforcing line forming protrusions 3 formed at intervals on the left and right sides of the rule line forming protrusion working 2 as the center.