Anodization of aluminum with restricted surface areas is reported in this study. Particularly, the side wall of aluminum thin film is anodized for the purpose of obtaining the confined number of pores with high aspect ratio. It has been observed that side wall anodization does not occur uniformly since the anodization speed is not uniform at the both interfaces and in the middle of the film. For this reason, the resultant pore front profile shows a parabolic shape, which resembles the parabolic velocity profile of fluid flow through two slabs. During the anodization process, the pores tend to break apart and the structure becomes more complex. Side wall anodization is investigated at various applied voltages and the resultant pore structures are shown.