1. An object detection method in which an electromagnetic wave is transmitted from transmission/reception means (M) to a predetermined area set in a direction in which a subject vehicle (Va) is running; a reflected wave produced by reflection of the electromagnetic wave off a target (Vb) is received; and at least a direction and a distance of the target (Vb) are detected on the basis of the received reflected wave, characterized by comprising: a first step of setting a dummy target in a direction which is the same direction as that of the detected target (Vb), and at a position whose distance is double that of the detected target (Vb); a second step of setting a second-order wave target detection area in a predetermined area including the position of the dummy target; a third step of judging the target (Vb), which is detected in the second-order wave target detection area, as being a second-order wave target; a fourth step of setting an interpolated target in a direction which is the same as that of the second-order wave target, and at a position whose distance is half that of the second-order wave target; a fifth step of setting a fundamental wave target detection region in a predetermined area including the position of the interpolated target; and a sixth step of outputting the interpolated target as a fundamental wave target in a case where no fundamental wave target is detected in the fundamental wave target detection region.