Provided are a re-wandering detecting device and method. The method includes: detecting an object and positional information about the object from an input image; determining 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 information about wandering of the object according to whether the object re-wanders.