1. A system for detecting an object from a depth image, the system comprising: a communication module; a memory configured to store an object detection program; and a processor configured to execute the object detection program, wherein by executing the object detection program, the processor extracts a first object area and a second object area from the depth image, based on a floor plane and an outer plane which is set with respect to the floor plane, the processor extracts a target area including pixels of the second object area which are spaced apart from the first object area by a predetermined interval, the processor samples a pixel, which is included in the second object area but is not included in the target area, to extract a floor area from the second object area, calculates distances between the plane extracted from the floor area and pixels having a same direction as a direction of the first object area, calculates a boundary value between the object and a floor based on the calculated distances, and extracts a foreground pixel from the target area, based on the calculated boundary value, and the second object area comprises the object and the floor and is disposed under the first object area.