The aims of this study were to evaluate the effects of different carbamide peroxide concentrations on surface structure changes of porcelain restorative materials. A total of 50 discs were made and divided into five groups each include 10 specimens. One group served as control and no bleaching agent was applied. Other groups were immersed in the bleaching gels with the concentration of 10% (Group 10), 15% (Group 15), 20% (Group 20), 35% (Group 35) for an average of 8 hours per day. The bleaching procedure was performed over a period of 21 days. The surface roughness values were measured by surface profilometry. Treated ceramic surfaces were examined by scaning electron microscopy (SEM) and atomic force microscopy (AFM). The data were analyzed by analysis of variance and post-hoc Tukey test. The results showed that higher concentration of carbamide peroxide gel effect the surface roughness of test specimens significantly. The highest surface roughness values were obtained in group 35 (0.57 ?m±0.19) and showed significantly different from group C (0.24 ?m±0.11) which was the lowest surface roughness values. The concentration of the carbamide peroxide bleaching agent used in this study affected the surface roughness of the porcelain test specimens. Ceramic restoration should be protected before any bleaching for preventing negative effects of agent on surface properties.