Based on the tight-binding model, the electronic structure of graphene doped with N atoms is investigated. Wave function of $2s$-, $2p$-states of non-interacting neutral C atoms are chosen. Within the calculation of the Hamiltonian matrix elements, the first three co-ordination spheres are taken into account. As found, the zones’ hybridization leads to a splitting of the energy spectrum of electrons in the Fermi energy region. With increasing of nitrogen-atoms’ concentration, the conductivity of graphene decreases. As the nitrogen atoms concentration increases, the electron density of states at the Fermi level increases; so, decreasing of conductivity is caused by much greater decrease of relaxation time of electron states.