To provide a method of preventing a shearing crack due to hydrogen in steel of a steel plate without lowering productivity.

The hydrogen concentration CHin shearing is obtained on the basis of a hydrogen ladle value in manufacturing a slab of the steel plate or a sheet steel hydrogen concentration CH0at the end of rolling estimated from the hydrogen ladle value by calculation. When the CHis equal to or more than an allowable value Climitdetermined for every material equality, after shearing, steel plate equal to or more than a clearance d1between an upper blade 2 and a lower blade 3 of a shearing machine is cut from the cut end part and removed. As the shearing machine, a plurality of shearing machines disposed in the direction of conveying the steel plate are used, which are constructed so that the upper blade is composed of two stages having a cutout part between them in the shearing direction, and the upper stage side of the upper blade and the cutout part can further cut the cut end of the steel plate to a length equal to a clearance between the lower blade and the low stage side of the upper blade at least.

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