A motor drive according to the present invention includes an inverter, a motor rotational speed obtaining unit, a motor inertia information storage unit, a motor rotational energy calculator, a dynamic braking circuit, a tolerance information storage unit for storing the tolerances of resistors of the dynamic braking circuit, a power element operation unit, a dynamic braking circuit operation unit, and a tolerance comparator for performing a comparison between the rotational energy of a motor and the tolerance of the dynamic braking circuit. When the rotational energy exceeds the tolerance, power elements of one of arms are turned on, while power elements of the other arm are turned off, without actuating the dynamic braking circuit. When the rotational energy is equal to or less than the tolerance, the dynamic braking circuit is actuated, and the power elements of the one of the arms are turned off.