We report on the thermal conductance of electrons in ballistic nanowires at low temperatures. The thermal conductance is calculated using the single-particle formalism taking into account local maxima in the dispersion relation. As the chemical potential increases,the thermal conductance follows the step- like quantization of the electric conductance that is dependent on the direction of the magnetic field. Results indicate that the Wiedemann–Franzlaw is violated at the jump of the electric conductance at very low temperatures.