Provided is a hard-top loose-leaf plate structure device for a rear compartment of a pickup truck which includes: a main aluminum extrusion strip; a right aluminum extrusion strip which is inserted in a right circular slot on the right of the main aluminum extrusion strip and is freely rotated at 90° or placed flat at 180° on a right circular lug of the main aluminum extrusion strip; a left aluminum extrusion strip which is inserted in a left circular slot on the left of the main aluminum extrusion strip and is freely rotated at 90° or placed flat at 180° on a left circular lug of the main aluminum extrusion strip; and a T-fixing strip.