To provide a trimming device for accurately cutting into strip a running steel plate by minimizing clearance variation generated in cutting by backlash between round cutters during trimming work, in the trimming device for cutting the end of the steel plate into strip between the round cutters having an upper blade and a lower blade.

This trimming device for cutting the steel plate into strip with a round blade comprises a clearance adjusting device for adjusting a clearance between the upper blade and the lower blade, a shaft movement constraining device for constraining axial movement by pulling a rotating shaft of the cutter on the side having the clearance adjusting device or pressing it, and preferably a hydraulic jack. By providing the shaft movement constraining device, the clearance variation generated during trimming by backlash of the clearance adjusting device is prevented, and operation load of a clearance variation preventing device is eliminated.