To provide a sharpener for a cutter, simply sharpening a cutter.

This sharpener for a cutter is provided with a sharpening part including: at least two plate parts 34a, 34b respectively having a polishing surface 36 on one side and disposed in alignment with each other in the width direction so that seen in the width direction, the polishing surfaces 36 intersect each other; an intersecting area moving means disposed on each one end side of the plate parts 34a, 34b to be movable in the longitudinal direction of the plate parts 34a, 34b in the intersecting area where the polishing surfaces 36 intersect each other; and a support part supporting the plate parts 34a, 34b on one end side.