A method of manufacturing a thin support package structure includes the steps of: preparing a support plate formed with a plurality of grooves adjacent to an outer rim thereof, forming a releasing material layer on the support plate; forming a first circuit layer on the releasing material layer so as to form a thin circuit board; forming a dielectric layer on the releasing material layer; forming a plurality of openings in the dielectric layer; forming a second circuit layer on the dielectric layer; forming connection plugs by filling the openings; forming a solder mask on the dielectric layer; forming a plurality of notches on the lower surface of the support plate to communicate with the grooves, respectively; and removing the central part of the support plate between the notches and the central part of the releasing material layer on the support plate.