To provide a desirable crop shear method and a desirable crop shear apparatus device which realize smooth crop shear by suppressing the occurrence of the error about crop length without using special detecting means.

In this crop shear method, the plane shape of a metal plate A is recognized by using a planar shape recognizing means 20 and the crops Aa, Ab of the metal plate A are cut off with a shear means 40. In such a case, the crop lengths La, Lb to be sheared are finally determined (a) after determining the lengths on the basis of the plane shape of the metal plate A which is grasped with the plane shape recognizing means 20 and (b) by making correction to the length, the correction with the deformation of the metal plate A which is separately grasped taken into consideration.