To dispense with obtaining the working condition every time when the width of a strip or the material of the strip is changed, and to reduce the setup time by specifying the position of laser beam irradiation when a part in the vicinity of a tip of a crack in the strip having an edge crack is heated with a pulse point heat source to expand the crack, and the strip is split thereby.

When a strip is split, the position of the laser beam irradiation is determined as follows. The value 4κt/W2 is set, where W is the distance from the split line to upper and lower edges of the strip, κ is the coefficient of thermal expansion of the material of the strip, and (t) is the heating time of the pulse laser. The value D/W=0.1 when the set value is 0.0001-0.05; the value D/W=0.2 when the set value is 0.05-1.0, and the value D/W=0.4 when the set value is ≥1.0, where D is the distance of the center position of the laser beam point heat source from the tip of the edge crack. The position of laser beam irradiation is set to the position of the corresponding D/W. The setup time is short, the heating point is best, and the splitting work does not take time, and can be automatic.