A vehicle obstacle detection device, comprising: a sensor configured to intermittently transmit transmission waves and receive reflected waves that are generated by reflection of the transmission waves; and a controller configured to output a transmission signal for instructing the sensor to transmit the transmission waves, the controller being configured to evaluate, when the sensor receives the reflected waves with amplitude that is higher than or equal to a prescribed threshold (Th), a time period between a timing of outputting the transmission signal and a timing of reception of the reflected waves by the sensor, to detect presence or absence of an obstacle, wherein the sensor is configured to be driven with a power supply voltage to output the transmission waves, and characterized in that the controller comprises a voltage monitoring unit that is configured to detect the power supply voltage, the controller being configured to more reduce the prescribed threshold (Th) as the power supply voltage detected by the voltage monitoring unit is lower, wherein the controller is configured to change the prescribed threshold (Th), in stages, according to the power supply voltage detected by the voltage monitoring unit, wherein the prescribed threshold (Th) includes a first threshold and a second threshold that is more than the first threshold, and wherein the controller is configured to select, as the threshold (Th), any one of the first and second thresholds (Th1, Th2), according to the power supply voltage value (Vs), and wherein the controller comprises a microcomputer, which is configured to detect, when the power supply voltage is equal to or more than a first reference value and is less than a second reference value, the presence or absence of the obstacle with the first threshold, the controller being configured to detect, when the power supply voltage is equal to or more than the second reference value and is less than a third reference value, the presence or absence of the obstacle with the second threshold. a sensor configured to intermittently transmit transmission waves and receive reflected waves that are generated by reflection of the transmission waves; and a controller configured to output a transmission signal for instructing the sensor to transmit the transmission waves, the controller being configured to evaluate, when the sensor receives the reflected waves with amplitude that is higher than or equal to a prescribed threshold (Th), a time period between a timing of outputting the transmission signal and a timing of reception of the reflected waves by the sensor, to detect presence or absence of an obstacle, wherein the sensor is configured to be driven with a power supply voltage to output the transmission waves, and characterized in that the controller comprises a voltage monitoring unit that is configured to detect the power supply voltage, the controller being configured to more reduce the prescribed threshold (Th) as the power supply voltage detected by the voltage monitoring unit is lower, wherein the controller is configured to change the prescribed threshold (Th), in stages, according to the power supply voltage detected by the voltage monitoring unit, wherein the prescribed threshold (Th) includes a first threshold and a second threshold that is more than the first threshold, and wherein the controller is configured to select, as the threshold (Th), any one of the first and second thresholds (Th1, Th2), according to the power supply voltage value (Vs), and wherein the controller comprises a microcomputer, which is configured to detect, when the power supply voltage is equal to or more than a first reference value and is less than a second reference value, the presence or absence of the obstacle with the first threshold, the controller being configured to detect, when the power supply voltage is equal to or more than the second reference value and is less than a third reference value, the presence or absence of the obstacle with the second threshold.