The invention provides a cutter adjusting jig and a cutter adjusting method. The cutter adjusting jig is simple in structure, capable of rapidly and accurately adjusting the stretching amount of a cutter in a cutter clamping device, lighter in weight and lower in cost. The cutter adjusting jig is adopted in the cutter adjusting method. The cutter clamping device is fixed between a base and a positioning block of the cutter adjusting jig, the cutter clamping device and the cutter abut against the positioning block through a first screw and a second screw respectively, and therefore the stretching amount of the cutter can be adjusted, and the cutter needing to be adjusted can be freely selected. The operating procedure of the cutter adjustment is simplified, the work efficiency is improved, and the stretching amount of the cutter can be adjusted by freely replacing the positioning block. The cutter adjusting jig and the cutter adjusting method can be suitable for different work environments, and the cutter can be adjusted only by screwing the screws by hand.