A vehicle-mounted radar apparatus for transmitting radar waves toward the outside of a vehicle mounting the apparatus thereon and receiving the radar waves reflected from an object to thereby acquire information about the object. In the apparatus, a target detection unit transmits and receives the radar waves to detect positions of targets. An object position determination unit determines a position of the object reflecting the radar waves on the basis of the positions of the targets. A representative target selection unit selects a representative target from the targets. A same-object target selection unit selects targets belonging to the same object as the representative target. A large-vehicle determination unit determines whether or not the object is a large vehicle on the basis of a number of targets selected by the same-object target selection unit and reflection wave received powers for the respective targets.