The spin-splitting energies of the conduction band for ideal wurtzite materials are calculated within the nearest-neighbor tight-binding method. It is found that ideal wurtzite bulk inversion asymmetry yields not only a spin-degenerate line (along the kz axis) but also a minimum-spin-splitting surface, which can be regarded as a spin-degenerate surface in the form of bkz2−k‖2 = 0 (b ≈ 4) near the Γ point. This phenomenon is referred to as the Dresselhaus effect (defined as the cubic-in-k term) in bulk wurtzite materials because it generates a term γwz(bkz2−k‖2)(σxky−σykx) in the two-band k∙p Hamiltonian.