In a nitride semiconductor device having an active layer 12 between a
first electrically conductive type of layer and a second electrically
conductive type of layer, a quantum well structure is adopted in which an
active layer 12 has at least a well layer 11 formed of a nitride
semiconductor containing In and Al and a barrier layer 2 formed of a
nitride semiconductor containing Al, whereby a laser device excellent in
emitting efficacy at a short wavelength region is obtained. It is
particularly preferable that said well layer 1 is formed of
Al.sub.xIn.sub.yGa.sub.1-x-yN (0