A capacitor capacitance measurement device comprising: a discharge circuit connected in parallel to a capacitor and configured by a discharge resistor and a discharge switch connected in series; a resistor voltage dividing circuit connected in parallel to the capacitor and configured by a first resistor and a second resistor connected in series; and a control device for discharging energy stored in the capacitor, by stopping charging of the capacitor and conducting the discharge switch, measuring a voltage at a voltage division point of the resistor voltage dividing circuit, and calculating a capacitor capacitance from the voltage at the voltage division point, wherein the capacitor is discharged for a predetermined time within a time taken until a voltage value of the capacitor which drops due to discharge of the energy stored in the capacitor reaches a predetermined value, a capacitor voltage calculated from the voltage, at the voltage division point of the resistor voltage dividing circuit, measured within the predetermined time is set as a measurement capacitor voltage, and a difference in the measurement capacitor voltage between measurement times within the predetermined time is compared with a preset threshold, and it is determined whether a value of the capacitor capacitance calculated by the control device is correct, or a straight line indicating a gradient of a fall in capacitor voltage is calculated by using an average, in the predetermined time, of the voltage at the voltage division point of the resistor voltage dividing circuit measured within the predetermined time, and an absolute value of a difference between the measurement capacitor voltage and a capacitor voltage on the straight line at the same time is compared with a preset threshold, and it is determined whether a value of the capacitor capacitance calculated by the control device is correct. a discharge circuit connected in parallel to a capacitor and configured by a discharge resistor and a discharge switch connected in series; a resistor voltage dividing circuit connected in parallel to the capacitor and configured by a first resistor and a second resistor connected in series; and a control device for discharging energy stored in the capacitor, by stopping charging of the capacitor and conducting the discharge switch, measuring a voltage at a voltage division point of the resistor voltage dividing circuit, and calculating a capacitor capacitance from the voltage at the voltage division point, wherein the capacitor is discharged for a predetermined time within a time taken until a voltage value of the capacitor which drops due to discharge of the energy stored in the capacitor reaches a predetermined value, a capacitor voltage calculated from the voltage, at the voltage division point of the resistor voltage dividing circuit, measured within the predetermined time is set as a measurement capacitor voltage, and a difference in the measurement capacitor voltage between measurement times within the predetermined time is compared with a preset threshold, and it is determined whether a value of the capacitor capacitance calculated by the control device is correct, or a straight line indicating a gradient of a fall in capacitor voltage is calculated by using an average, in the predetermined time, of the voltage at the voltage division point of the resistor voltage dividing circuit measured within the predetermined time, and an absolute value of a difference between the measurement capacitor voltage and a capacitor voltage on the straight line at the same time is compared with a preset threshold, and it is determined whether a value of the capacitor capacitance calculated by the control device is correct.