Aerodynamic characteristics of a High-Lift-Device (HLD) are investigated by CFD. A two-dimensional configuration with a slat and flap for a taking-off arrangement is simulated. The k-ω SST turbulence model is carefully incorporated with a mean flow to treat complex flows around HLD, which includes the interaction of the separated shear layer from a fore-wing and the boundary layer on the aft-wing. The results are compared with experimental data and a previously reported simulation. The lifts coincide among them before the stall angle and the drag components also agree reasonably with the referred computation.