A boost converter control apparatus which is configured to control a boost converter in a motor drive system, said motor drive system comprising: a direct current power supply; a three-phase alternating current motor; an electric power converter disposed between the direct current power supply and the three-phase alternating current motor, the electric power converter including switching circuits, each of which corresponds to respective one of three phases of the three-phase alternating current motor, and a smoothing condenser, which is disposed electrically in parallel with the switching circuits; and the boost converter disposed between the electric power converter and the direct current power supply, the boost converter boosting a direct current voltage of the direct current power supply and supplying it to the electric power converter, said boost converter control apparatus comprising: an operating device comprising a proportional element, an integral element and a derivative element, the derivative element being configured as a bandpass filter, said operating device calculating a PID controlled variable corresponding to an electric current command value of the boost converter for maintaining an output voltage of the boost converter at a command value of an inter-terminal voltage VH of the smoothing condenser; and a controlling device which is configured to control the output voltage of the boost converter on the basis of the calculated PID controlled variable, wherein said operating device calculates a PI controlled variable in which the derivative element is invalid, instead of the PID controlled variable, if a rotational speed of the three-phase alternating current motor is greater than or equal to a predetermined value, and said controlling device controls the output voltage on the basis of the calculated PI controlled variable. a direct current power supply; a three-phase alternating current motor; an electric power converter disposed between the direct current power supply and the three-phase alternating current motor, the electric power converter including switching circuits, each of which corresponds to respective one of three phases of the three-phase alternating current motor, and a smoothing condenser, which is disposed electrically in parallel with the switching circuits; and the boost converter disposed between the electric power converter and the direct current power supply, the boost converter boosting a direct current voltage of the direct current power supply and supplying it to the electric power converter, said boost converter control apparatus comprising: an operating device comprising a proportional element, an integral element and a derivative element, the derivative element being configured as a bandpass filter, said operating device calculating a PID controlled variable corresponding to an electric current command value of the boost converter for maintaining an output voltage of the boost converter at a command value of an inter-terminal voltage VH of the smoothing condenser; and a controlling device which is configured to control the output voltage of the boost converter on the basis of the calculated PID controlled variable, wherein said operating device calculates a PI controlled variable in which the derivative element is invalid, instead of the PID controlled variable, if a rotational speed of the three-phase alternating current motor is greater than or equal to a predetermined value, and said controlling device controls the output voltage on the basis of the calculated PI controlled variable. an operating device comprising a proportional element, an integral element and a derivative element, the derivative element being configured as a bandpass filter, said operating device calculating a PID controlled variable corresponding to an electric current command value of the boost converter for maintaining an output voltage of the boost converter at a command value of an inter-terminal voltage VH of the smoothing condenser; and a controlling device which is configured to control the output voltage of the boost converter on the basis of the calculated PID controlled variable, wherein said operating device calculates a PI controlled variable in which the derivative element is invalid, instead of the PID controlled variable, if a rotational speed of the three-phase alternating current motor is greater than or equal to a predetermined value, and said controlling device controls the output voltage on the basis of the calculated PI controlled variable.