A setting unit of an object existence determination apparatus sets an object-existence determination region with a lateral width in the travelling direction of an own vehicle using a lateral speed of a target object and a determination result by a straight-travel determining unit. An existence determining unit determines, based on the lateral position of the target object and the object-existence determination region, whether there is a possibility of at least part of the target object existing on a travelling course of the own vehicle. The setting unit sets the lateral width of the object existence determination region to be larger as the lateral speed becomes higher, and sets, upon determination that the own vehicle is not travelling straight, the lateral width of the object existence determination region to be smaller than the lateral width of the object-existence determination region used when the own vehicle is travelling straight.