1. A method of detecting re-wandering, the method comprising: detecting, by at least one processor, an object and positional information about the object from an input image; determining, by the processor, whether the object wanders based on the positional information about the object; in response to determining that the object wanders, determining whether the object re-wanders by determining whether a database stores information about an object identical to the object detected from the input image; and providing, by the processor, information about wandering of the object according to whether the object re-wanders.