1. A system for monitoring a queue, comprising: an image receiving unit that receives image information including depth information of objects and a background of a photographing space through a depth detection device; an object information collector that calculates actual heights of the objects using the depth information of the objects and the background obtained from the image information and initial parameters including a height and an angle measured by a sensing unit in the depth detection device; a filter that creates cluster set information composed of a plurality of items of cluster information calculated by filtering the objects in the image information to a plurality of different height values; and an object tracking unit that recognizes the objects by comparing the cluster set information with a predetermined pattern, assigns waiting time information for counting the time from the point of time when the objects are recognized, to the objects, and tracks the objects in the queue in accordance with the queue order.