A motor drive control device comprising: a rectifier configured to rectify an alternating-current voltage supplied from an alternating-current power supply; a boosting circuit including a reactor, a switching element, and a backflow preventing element and configured to boost a direct-current bus voltage supplied from the rectifier; a smoothing capacitor configured to smooth an output of the boosting circuit; an inverter circuit configured to convert the direct-current bus voltage smoothed by the smoothing capacitor into an alternating-current voltage and output the alternating-current voltage to a motor (81, 83); a boosting control unit configured to control an operation of the boosting circuit; an inverter control unit configured to control an operation of the inverter circuit; and a circuit protecting unit configured to suppress a ripple current flowing through the smoothing capacitor, the motor drive control device being characterized in that in the circuit protecting unit, a correlation of an on-duty ratio of the switching element included in the boosting circuit, output power of the inverter circuit, and an estimated ripple current being an estimate of the ripple current flowing through the smoothing capacitor is set, the circuit protecting unit including an inverter output power computing unit configured to compute the output power, and a ripple current estimating unit configured to determine an estimated ripple current being an estimate of the ripple current flowing through the smoothing capacitor on a basis of an on-duty ratio of the switching element determined by the boosting control unit, the output power computed by the inverter output power computing unit, and the correlation, the circuit protecting unit further including at least one of an on-duty ratio limiting unit configured to reduce the on-duty ratio of the boosting circuit to reduce an amount of boosting when the estimated ripple current determined by the ripple current estimating unit exceeds a preset threshold, and a rotation speed limiting unit configured to reduce the output power when the estimated ripple current determined by the ripple current estimating unit exceeds the threshold. a rectifier configured to rectify an alternating-current voltage supplied from an alternating-current power supply; a boosting circuit including a reactor, a switching element, and a backflow preventing element and configured to boost a direct-current bus voltage supplied from the rectifier; a smoothing capacitor configured to smooth an output of the boosting circuit; an inverter circuit configured to convert the direct-current bus voltage smoothed by the smoothing capacitor into an alternating-current voltage and output the alternating-current voltage to a motor (81, 83); a boosting control unit configured to control an operation of the boosting circuit; an inverter control unit configured to control an operation of the inverter circuit; and a circuit protecting unit configured to suppress a ripple current flowing through the smoothing capacitor, the motor drive control device being characterized in that in the circuit protecting unit, a correlation of an on-duty ratio of the switching element included in the boosting circuit, output power of the inverter circuit, and an estimated ripple current being an estimate of the ripple current flowing through the smoothing capacitor is set, the circuit protecting unit including an inverter output power computing unit configured to compute the output power, and a ripple current estimating unit configured to determine an estimated ripple current being an estimate of the ripple current flowing through the smoothing capacitor on a basis of an on-duty ratio of the switching element determined by the boosting control unit, the output power computed by the inverter output power computing unit, and the correlation, the circuit protecting unit further including at least one of an on-duty ratio limiting unit configured to reduce the on-duty ratio of the boosting circuit to reduce an amount of boosting when the estimated ripple current determined by the ripple current estimating unit exceeds a preset threshold, and a rotation speed limiting unit configured to reduce the output power when the estimated ripple current determined by the ripple current estimating unit exceeds the threshold.