PROBLEM TO BE SOLVED: To provide a cutter for observation surface that is durable and easily forms a hole with a flat observation surface without having to adjust tension, or the like.SOLUTION: The cutter 1 for an observation surface includes: an axial cutting blade 11 radially disposed between the tip ends of the cutter and whose cutting edge 13 is arranged facing in an axial direction an axial cutting cutter 10 having openings 19A and 19B formed on the both sides of the axial cutting blade 11 serving as a boundary line and a radial cutting blade 21 placeable on the back side of the axial cutting blade 11 of the axial cutting cutter 10, and rotatable about an axis parallel to an axis S of the axial cutting cutter 10 while the cutting edges 23 thereof faces in the radial direction.
