We investigate the effect of excitons on the photo-absorption in the solar-cell with AlGaAs/GaAs superlattice active layer. Absorption spectrum measured at room temperature is analyzed by using numerical simulation. Experimentally obtained spectrum is well explained by the simulation taking the excitonic effect into account. The photo-absorption is enhanced by excitons especially near the absorption edge due to the discrete bound exciton states as well as unbound continuous sates. This result clearly indicates that the excitonic absorption is effective in the superlattice even at room temperature. Superlattice active layer enhances the absorption efficiency of solar-cells and very useful for device applications. (C) 2011 Published by Elsevier B.V.