The invention discloses a cutting tool of a paper shredder, which comprises a pair of cylindrical rolling cutter wheels parallelly arranged on a tool rest to be rotated in the reverse direction. The invention is characterized in that: a. at least a linear planar hard guide cutting disc is penetrated on two cutter shafts of the middle parts of the two cylindrical rolling cutter wheels with a movable fit; b. bayonets which can be clamped by the both side slot walls of a strip-shaped slot of a surface cover are opened on the hard guide cutting disc along the central line part; c. concave cuttingedges which can cut the paper are formed at the bottom parts of the bayonets; and d. straight cutters which are tangential with the cutting edges are respectively arranged on one side of the two cutter shafts which are tightly close to the guide cutting disc with a tight fit. The cutting tool of the paper shredder can overcome the phenomenon of cutter blocking between the two cylindrical rolling cutter wheels due to too much paper involving in a notch of the tool, thus being conducive to the normal operation of the paper shredder and the improvement of the shredding effect; the bayonets of theguide cutting disc are clamped by the both side slot walls of the strip-shaped slot of the opposite plastic surface cover, thus avoiding the phenomenon of propping up the strip-shaped slot due to toomuch paper introduced.