Method for producing group-iii nitride semiconductor laser element

A method for producing a group-III nitride semiconductor laser element using a semipolar surface is provided. A resonator mirror capable of reducing an oscillation threshold current is stably supplied. A support plate (H) is inclined at an angle (THETA) toward a reference plane (Ab) defined by a pressing direction (PR) and an a-axis from an m-axis on a c-m plane from the state in which the pressing direction (PR) and the surface (Ha) of the support plate (H) are orthogonal to each other, and further a blade (5g) is positioned so as to overlap a plane including an intersecting portion (P1) of an endmost scribe mark (5b1) among a plurality of scribe marks (5b) and the surface (5a) of a substrate product (5) and extending along the pressing direction (PR). When an angle (ALPHA) is within the range of 71 DEG -79 DEG C or within the range of 101 DEG -109 DEG , the angle (THETA) falls within the range of 11 DEG -19 DEG , and therefore the reference plane (Ab) extending along the pressing direction (PR) extends along a c-plane orthogonal to a c-axis.