To provide a knife blade of a cutter knife with which, when the knife blade is broken off or is broken in the middle, there exists no possibility of scattering of the broken part and safety of the cutter knife is improved and fear sensation when it is used can be wiped out.

In the knife blade A of the cutter knife, a cutting edge 1 is provided lengthwise on one side edge and folding lines 2 inclined in the width direction provided lengthwise at definite intervals are provided, and when a top cutting edge becomes dull, a front part from a part of the folding line 2 is removed, a connecting member 7 which successively makes partition blades (a) divided by the folding lines 2 under a connected condition is provided on the side face of the knife blade A, and the broken part of the knife blade (a) is left to be connected with the knife blade (a) on the holder (b) side with the connecting member 7, and there exists no possibility of scattering or falling down of the broken part.