A motor drive control apparatus, comprising: a rectifier to rectify an AC voltage supplied from an AC source; a booster circuit including a reactor, a switching element, and a backflow preventing element, the booster circuit being configured to boost a DC bus voltage supplied from the rectifier; a smoothing capacitor to smooth an output of the booster circuit; an inverter circuit to convert the DC bus voltage smoothed by the smoothing capacitor into an AC voltage and supply the AC voltage to a motor; a boost control unit to control operation of the booster circuit; an inverter control unit to control operation of the inverter circuit; a DC bus voltage detection unit to detect the DC bus voltage supplied from the booster circuit; characterized by a boosting operation stop determination unit to determine whether or not to perform a stopping operation of a boosting operation in the booster circuit, the inverter control unit being configured to control, while the boost control unit is controlling the booster circuit to perform the stopping operation of the boosting operation, the inverter circuit to fix a rotation speed of the motor when the DC bus voltage (Vdc) supplied from the booster circuit is increasing, the boosting operation stop determination unit is configured to determine whether or not to perform the stopping operation of the boosting operation based on a modulation degree of the conversion by the inverter control unit from the DC bus voltage (Vdc) into the AC voltage, the modulation degree being stored as a reference modulation degree (Ks) at a time when a starting operation of the boosting operation is completed by reaching a final target voltage value for the DC bus voltage (Vdc), and the reference modulation degree (Ks) being updated at a time when the starting operation of the boosting operation is completed again, wherein, if the modulation degree is less than the reference modulation degree (Ks), the booster circuit stops the boosting operation. a rectifier to rectify an AC voltage supplied from an AC source; a booster circuit including a reactor, a switching element, and a backflow preventing element, the booster circuit being configured to boost a DC bus voltage supplied from the rectifier; a smoothing capacitor to smooth an output of the booster circuit; an inverter circuit to convert the DC bus voltage smoothed by the smoothing capacitor into an AC voltage and supply the AC voltage to a motor; a boost control unit to control operation of the booster circuit; an inverter control unit to control operation of the inverter circuit; a DC bus voltage detection unit to detect the DC bus voltage supplied from the booster circuit; characterized by a boosting operation stop determination unit to determine whether or not to perform a stopping operation of a boosting operation in the booster circuit, the inverter control unit being configured to control, while the boost control unit is controlling the booster circuit to perform the stopping operation of the boosting operation, the inverter circuit to fix a rotation speed of the motor when the DC bus voltage (Vdc) supplied from the booster circuit is increasing, the boosting operation stop determination unit is configured to determine whether or not to perform the stopping operation of the boosting operation based on a modulation degree of the conversion by the inverter control unit from the DC bus voltage (Vdc) into the AC voltage, the modulation degree being stored as a reference modulation degree (Ks) at a time when a starting operation of the boosting operation is completed by reaching a final target voltage value for the DC bus voltage (Vdc), and the reference modulation degree (Ks) being updated at a time when the starting operation of the boosting operation is completed again, wherein, if the modulation degree is less than the reference modulation degree (Ks), the booster circuit stops the boosting operation.