A semiconductor laser, a semiconductor device and a nitride series III-V group compound substrate capable of obtaining a crystal growth layer with less fluctuation of the crystallographic axes and capable of improving the device characteristics, as well as a manufacturing method therefor are provided. The semiconductor laser comprises, on one surface of a substrate used for growing, a plurality of spaced apart seed crystal layers and an n-side contact layer having a lateral growing region which is grown on the basis of the plurality of seed crystal layers. The seed crystal layer is formed in that a product of width w1 (unit: &mgr;m) at the boundary thereof relative to the n-side contact layer along the arranging direction A and a thickness t1 (unit: &mgr;m) along the direction of laminating the n-side contact layer is 15 or less. A semiconductor layer comprising a nitride series III-V group compound semiconductor is laminated on a substrate 11 comprising an n-type GaN. Protruded seed crystal portions are formed and a growth suppression layer having an opening corresponding to the seed crystal portion is disposed to the substrate. The semiconductor layer grows on the basis of the seed crystal portion and has a lateral growing region of low dislocation density.