We report calculations from first principles to determine the structural and electronic properties of ErB 2 compound using the Density Func- tional Theory (DFT) and the Full-Potential Linearized Augmented Plane Waves (FP-LAPW) method. For the description of the electron- electron interaction, the Generalized Gradient Approximation Perdew-Burke-Ernzerhof (GGA-PBE) and PBE0 Hybrid Functional were employed. From the density of states (DOS), it is found that the addition of a fraction of the exact Hartree-Fock exchange energy, in the PBE approximation, evidence the localization of the 4f -Er orbitals, which favors electronic spin polarization of these orbitals in the ErB 2 compound. The PBE0 scheme is justified because it best describes the electronic and magnetic properties of strongly correlated systems than the PBE approximation.