A hooking structure disposed on a door of a vehicle ensures safety of a passenger by preventing the door from being pushed inside in a side collision of the vehicle, by fastening a hooking structure integrally formed with the lower end of the door. The hooking structure may include: a welding flange that is fastened in parallel to an inner panel of a vehicle door; a hooking flange formed perpendicularly to an outer panel of the vehicle door; a connecting portion integrally connecting the welding flange with the hooking flange; a first closed-section flange disposed in an inverted wall shape between the welding flange and the connecting portion; and a second closed-section flange disposed in an inverted wall shape between the hooking flange and the connecting portion.