In this study, we report electrochemical synthesis of Sn oxides with dual-pore structure by employing anodic oxidation without the use of a porous template. As-prepared Sn oxide layers contain hemispherical micropores of less than 2μm diameters and nanopores of less than 50nm diameters. The formation and size of the micropores strongly depended on the thickness of the Sn layer and the type of the underlying substrate. A two-step anodic oxidation process produced a completely open pore structure, resulting in robust interconnections between the micropores and nanopores. The tensile stresses originating from the anodized Sn oxide and the associated local distortion of the Sn metal underneath it are the likely driving forces for the formation of micropores.