A combination furniture includes a base, a main cushion, two armrests, a backrest, and a fastener assembly. The top surface of the base is concavely provided with plural strip-shaped coupling grooves. The main cushion has a bottom plate provided with plural coupling strips integrally projecting from the bottom plate for being coupled with the coupling grooves. The two armrests have a pair of combining parts formed in parallel and slidingly and transversely installed on two sides of the base, respectively. The backrest has a pair of fixing parts formed on the backrest in parallel for correspondingly overlapping the two combining parts of the two armrests. The fastener assembly fastens the combining parts and the corresponding fixing parts to the base. Therefore, the combination furniture is easily assembled, manufactured, and transported.