The charge transport mechanism in thick film (~ 100 nm) amorphous boron nitride (a-BN) was studied experimentally and theoretically. Applying the experiments on the injection of minor carriers of n- and p-type silicon, the contribution of electrons and holes to the a-BN conductivity in the Si/BN/Al structure was determined. It was established that electrons and holes contribute to the a-BN conductivity, i.e. the a-BN conductivity is two-band. In a broad range of electric fields and temperatures, the charge transport in a-BN is satisfactorily described in the framework of the multiphonon trap ionization theory with thermal WT = 1.0 eV and optical Wopt = 2.0 eV trap ionization energies, respectively.