An object detection device includes: a transmission/reception unit that has a vibrator capable of transmitting and receiving ultrasound, that causes the vibrator to transmit transmission signals at different timings, and that receives the reception signals returning after being reflected on a circumferentially existing object; an acquisition unit that acquires a first distance to the object, based on a time difference between a transmission timing of a first transmission signal and a reception timing of a first reception signal, and that acquires a relative speed of the object, based on a frequency difference between the first transmission signal and the first reception signal; an estimation unit that estimates a second distance to the object at a transmission timing of a second transmission signal to be transmitted subsequently to the first transmission signal; and an adjustment unit that adjusts the number of waves or a transmission time of the second transmission signal.