An object detection device includes: first and second transmission/reception units transmitting and receiving an exploration wave to detect a peripheral object; and a processing unit determining a position of an object based on reception results of the first and second transmission/reception units. The processing unit calculates a first point based on first and second exploration waves, calculates a second point based on third and fourth exploration waves, determines that the object exists on a line segment interconnecting the first and second points when a distance between the first and second points is less than a predetermined value, and determines that the object exists on the line segment and line segments extended from both ends of the line segment when the distance between the first and second points is equal to or greater than the predetermined value.