In a warning apparatus, a restriction unit performs restriction of the issuance of a warning about a ghost from an issuing unit. A trajectory calculator calculates an estimated trajectory of each of first and second target objects. A cancelling unit cancels the restriction of the issuance of the warning about the ghost from the issuing unit upon determination that a predetermined cancelation condition is satisfied for the first and second target objects. The cancelation condition includes a condition that a passing distance between the first and second target objects is larger than a predetermined distance threshold.