DIAMOND SUBSTRATE PRODUCING METHOD

A diamond substrate producing method includes a belt-shaped separation layer (22) forming step of applying a laser beam to a diamond ingot (2) as relatively moving the diamond ingot (2) and a focal point of the laser beam in a [110]-direction perpendicular to a (110)-plane, thereby forming a belt-shaped separation layer (22) extending in the [110]-direction inside the diamond ingot (2), an indexing step of relatively moving the diamond ingot (2) and the focal point in an indexing direction parallel to a (001)-plane and perpendicular to the [110]-direction, a planar separation layer (24) forming step of repeating the belt-shaped separation layer (22) forming step and the indexing step to thereby form a planar separation layer (24) parallel to the (001)-plane inside the diamond ingot (2), the planar separation layer (24) being composed of a plurality of belt-shaped separation layers (22) arranged side by side in the indexing direction, and a separating step of separating a diamond substrate (34) from the diamond ingot (2) along the planar separation layer (24). The most suitable drawing: FIG. 2B.