In order to investigate the effects of vortex control by deflecting flaps on the improvement of the aerodynamics of highly swept wings at large incidence, comparison of the experimental and numerical studies was conducted for a 74° delta wing equipped with an apex flap and leading-edge flaps. In the experimental study, flow visualization and force measurement were employed and in the numerical study the pseudo-compressibility method was utilized to solve the 3-D incompressible Navier-Stokes equations. The flow visualization and numerical simulation show that two vortex systems generated on the apex flap and leading-edge flaps interact in the form of mergence, and the downward deflection of the apex flap enhances the strength and delays the breakdown of the prime vortex at large incidence. The comparison of the aerodynamic characteristics illustrates that there are advantageous effects of deflecting flaps downward on the control of vortices.