PURPOSE: To improve cracking accuracy and to improve a cracking speed by forming an energy beam to a beam aligned to a desired cracking line and irradiating a work with the beam, thereby cracking the work.

CONSTITUTION: The energy beam is oscillated by a beam generator 1, such as laser, and after the oscillated energy beam is subjected to energy adjustment with an attenuator 2, the energy beam is made uniform by a beam homogeneizer 3. The beam made uniform by the beam homogeneizer 3 is passed through a mask 4 and the mask image is made into the linear beam aligned to the desired cracking line by a total reflection mirror 6 of an imaging lens system 5. The linear beam is imaged on the work 7. As a result, the exacter control of the beam by the cracking direction is made possible and the cracking of the work to a wire shape with high accuracy is made possible. The cracking accuracy is thus improved.