An object detection device includes: a transceiver section that transmits an ultrasonic wave and receives an ultrasonic wave including a reflected wave of the transmitted ultrasonic wave, and outputs a signal in accordance with a wavelength of the received ultrasonic wave; a frequency control section that changes a frequency of the ultrasonic wave transmitted by the transceiver section to a plurality of frequencies different from a driving frequency used to detect the distance from the object; and a fault determination section that determines whether a fault occurs in the function of detecting the distance from the object due to a value of an environment temperature or a wavelength of the ultrasonic wave transmitted by the transceiver section, based on a value of the signal outputted from the transceiver section when the transceiver section transmits the ultrasonic wave at a selected one of the frequencies different from the driving frequency.