A motor drive controller, for supplying output of a dc power source to a motor through an inverter and controlling drive of a motor, comprising: a converter for voltage converting output voltage from the dc power source for supply to the inverter; and a control section for controlling supply current to the motor through PWM control of the inverter, the converter comprising: a reactor connected at one end to the dc power source, and at least two switching elements ( Q1, Q2) connected in series, wherein an upper switching element connects to a power source side of the inverter and a lower switching element connects to an earth side of the inverter, and the other end of the reactor is connected to an intermediate point of the two switching elements (Q1, Q2), characterized in that the control section is adapted to calculate an inverter input voltage target value appropriate to efficient motor drive based on a rotational speed of the motor and a target output torque, and to perform PWM control of the converter switching elements in order to achieve the input voltage target value for an inverter input voltage, wherein a separate inverter for supplying current to a separate motor is connected to the output of the converter, and the control section is adapted to output a higher voltage of two inverter input target voltages calculated from rotational speeds and target outputs of the two motors (M1, M2). a converter for voltage converting output voltage from the dc power source for supply to the inverter; and a control section for controlling supply current to the motor through PWM control of the inverter, the converter comprising: a reactor connected at one end to the dc power source, and at least two switching elements ( Q1, Q2) connected in series, wherein an upper switching element connects to a power source side of the inverter and a lower switching element connects to an earth side of the inverter, and the other end of the reactor is connected to an intermediate point of the two switching elements (Q1, Q2), characterized in that the control section is adapted to calculate an inverter input voltage target value appropriate to efficient motor drive based on a rotational speed of the motor and a target output torque, and to perform PWM control of the converter switching elements in order to achieve the input voltage target value for an inverter input voltage, wherein a separate inverter for supplying current to a separate motor is connected to the output of the converter, and the control section is adapted to output a higher voltage of two inverter input target voltages calculated from rotational speeds and target outputs of the two motors (M1, M2). a reactor connected at one end to the dc power source, and at least two switching elements ( Q1, Q2) connected in series, wherein an upper switching element connects to a power source side of the inverter and a lower switching element connects to an earth side of the inverter, and the other end of the reactor is connected to an intermediate point of the two switching elements (Q1, Q2), characterized in that the control section is adapted to calculate an inverter input voltage target value appropriate to efficient motor drive based on a rotational speed of the motor and a target output torque, and to perform PWM control of the converter switching elements in order to achieve the input voltage target value for an inverter input voltage, wherein a separate inverter for supplying current to a separate motor is connected to the output of the converter, and the control section is adapted to output a higher voltage of two inverter input target voltages calculated from rotational speeds and target outputs of the two motors (M1, M2).