A laser diode device capable of obtaining high light efficiency and improving output by using an AlGaInN compound semiconductor as a material is provided. The laser diode device includes semiconductor layer which has an active layer and is made of a nitride Group III-V compound semiconductor containing at least one of aluminum (Al), gallium (Ga), and indium (In) among Group 3B elements and nitrogen (N) among Group 5B elements. The active layer has a strip-shaped light emitting region whose width W is from 5 .mu.m to 30 .mu.m, length L is from 300 .mu.m to 800 .mu.m, and output of laser light from the active layer is 200 mW or more.