A surrounding moving object detector includes a vehicle traveling information acquiring unit, a contact detection unit, a surrounding object information acquiring unit, a traveling course prediction processor, a contact possibility calculation processor, and a determination threshold changing processor. The traveling course prediction processor predicts a future traveling course of an vehicle based on vehicle traveling information acquired by the vehicle traveling information acquiring unit and predicts a future traveling course of a moving object present around the vehicle based on the surrounding object information acquired by the surrounding object information acquiring unit. The contact possibility calculation processor calculates a possibility of contact by comparing the future traveling course of the vehicle and the future traveling course of the moving object. The determination threshold changing processor changes a determination threshold based on the possibility of contact. The contact detection unit detects the contact based on the determination threshold.