Group-iii nitride semiconductor laser device

Provided is a group-III nitride semiconductor laser device having a structure capable of reducing malfunctions attributable to COD and mitigating a decline in heat dissipation capability. First and second cross-sections (27, 29), which are to become a laser resonator, intersect with an m-n plane. The group-III nitride semiconductor laser device (11) has a laser waveguide that extends in the direction of a cross line between the m-n plane and a semipolar plane (17a). The cross-sections (27, 29) are different from cleavage planes such as a c-plane, an m-plane and an a-plane. A semiconductor region (19) includes first through third regions (19b-19d) that extend in the direction of a waveguide vector (LGV). An aperture (31a) of an insulating film (31) is positioned above a ridge structure of the third region (19d) of the semiconductor region (19). At an electrode (15), first through third electrode sections (18b-18d) of a pad electrode (18) are respectively provided above the first through third regions (19b-19d) of the semiconductor region (19). The first electrode section (18b) has an arm section (18b_ARM1) that reaches an edge of the cross-section (27).