To provide a scribing apparatus in which a modified part can be formed with good accuracy of position.

Scribing is made by forming the modified part through irradiating laser light from a laser light source 2 and condensing the light into the inside of a work 10 through a condensing lens 9. The distance between the condensing lens 9 and the work 10 is measured by a length measurement device 12 for forming the depth of the modified part from the surface of the work 10 with good accuracy. The distance between the condensing lens 9 and the work 10 is brought near the set value by moving the work 10 in the direction of an optical axis 8 by a distance corresponding to the difference from the set value. Wherein the distance between the condensing lens 9 and the work 10 is brought near the set value by moving the work 10 through actuating an interval adjusting table 22.

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