present invention relates to a composite beam in which a fabricated truss is embedded in the concrete and more particularly it relates to a composite beam in which the fabricated truss acts as a truss beam which endures the concrete weight and the construction load in the liquid phase before the curing of the concrete and acts as a main structural member together with the concrete after the curing of the concrete application_number US 201615108290 A description although the present invention will be described in detail below with reference to the accompanying drawings the suggested embodiments are only for exemplification of the present invention for the definite understanding of the present invention and the present invention is not limited to them fig1 is an exploded perspective view of a flush type fabricated truss composite beam attached with a sheathing board according to an embodiment of the present invention and fig2 is a sectional view the flush type fabricated truss composite beam attached with the sheathing board according to the present invention largely comprises a fabricated truss 10 a sheathing board 20 and a concrete 30 the fabricated truss 10 is consisted of a truss member consisting of a lower chord a web member and an upper chord and the lower chord 110 of the fabricated truss 10 according to the present invention is consisted in a plate shape of a predetermined thickness and to the lower chord are combined screw rods 140 with a predetermined spacing along a length direction in a direction normal to.