A determining method for obstacles includes determining whether an ultrasonic noise exists in TOF of an ultrasonic wave reflected by an object and received; generating a virtual object on an outline of a parking path that a vehicle is to move on based on the received ultrasonic wave TOF; generating virtual indirect wave TOF using the virtual object; and determining whether the object is located inside or outside the outline of the parking path by comparing real indirect wave TOF, which is indirect wave TOF among the received ultrasonic wave TOFs, with the virtual indirect wave TOF.