This study investigated the effect of three bleaching agents (Whiteness Perfect, Whiteness Super, Whiteness HP) on roughness of three dental resin composites (Admira, Durafill VS, Gradia Direct). Twenty disk-shaped standard specimens (102mm) of each composite material were prepared and divided into four subgroups (n=5). In each resin composite group, the unbleached specimens served as control; the other specimens were bleached with one of the bleaching agents according to the manufacturer's instruction. Roughness values were assessed using the atomic force microscope and metallographic microscope. Two-dimensional and 3D images were also taken for detecting surface alterations of each specimen group. Although the surfaces of all specimens did not seem to be smooth, the unbleached control specimens showed more irregular areas compared with those of the bleached ones. Roughness values were decreased in bleached groups to some extent depending on the bleaching agents used.