A nitride-based semiconductor element having superior mass productivity and excellent element characteristics is obtained. This nitride-based semiconductor element comprises a substrate comprising a surface having projection portions, a mask layer formed to be in contact with only the projection portions of the surface of the substrate, a first nitride-based semiconductor layer formed on recess portions of the substrate and the mask layer and a nitride-based semiconductor element layer, formed on the first nitride-based semiconductor layer, having an element region. Thus, the first nitride-based semiconductor layer having low dislocation density is readily formed on the projection portions of the substrate and the mask layer through the mask layer serving for selective growth. When the nitride-based semiconductor element layer having the element region is grown on the first nitride-based semiconductor layer having low dislocation density, a nitride-based semiconductor element having excellent element characteristics can be readily obtained. The first nitride-based semiconductor layer is formed through only single growth on the substrate, whereby a nitride-based semiconductor element having excellent mass productivity is obtained.