To enhance the core heating efficiency in electron-driven fast ignition, we propose fast-electron beam guiding using externally applied longitudinal magnetic fields. Based on particle-in-cell simulations for FIREX-class experiments, we demonstrate sufficient beam guiding performance in collisional dense plasma by kilotesla-class external magnetic fields for the case with moderate mirror ratio (⩽10). Boring of the mirror field was found through the formation of magnetic pipe structure due to the resistive effects, which indicates a possibility of beam guiding in high mirror field for higher laser intensity and/or longer pulse duration.