A density functional theory is proposed for an inhomogeneous mixture system, which is based on the universality of the free energy density functional. The present formalism requires as input only the second-order direct correlation function and bridge function of the corresponding uniform fluid mixture. Applicability of the density functional theory was verified by applying the formalism to study on the structure of binary hard-sphere fluid mixture near a hard-planar wall; the predictions of the theory compare well with the corresponding computer simulation results.