To provide a ruling device which can apply a ruled line and enables exact and sure bending.

A ruling push blade (11) is attached to a mold (10) while a flat elastic part (25) which can be deformed elastically corresponding to the relative pushing force between the elastic part (25) and the tip part of the blade (11) is formed to the surface of a face plate (20). The ruling push blade (11) is relatively pressed to corrugated cardboard (30) so as to elastically deform the elastic part (25) by the relative approach of the tip part of the blade (11) and the elastic part (25) to form a recessed ruled line (45) to the corrugated cardboard (30) on the side of the blade (11) while forming a protruded ruled line (46) to the corrugated cardboard (30) on the side of the elastic part (25).