A reflection-point estimation section constituting an object detection apparatus first calculates a rotational correction angle for each estimated reflection point Pn by using the following equation, using the fact that the ratio of the amount of change in a detected distance dn to a movement amount In of a sonar is nearly equal to a tangent with respect to the direction normal to the surface of an object: Rotational correction angleφ=atan{(dn+1−dn)/In} in which n is a natural number. Subsequently, the reflection-point estimation section obtains estimated reflection points Pn′ after correction, by rotating each estimated reflection point Pn based on the calculation result.