Self-Duality of Super D3-brane Action on $AdS_{5}\times S^{5}$ Background

We show that the super D3-brane action on $AdS_5 \times S^5$ background recently constructed by Metsaev and Tseytlin is exactly invariant under the combination of the electric-magnetic duality transformation of the worldvolume gauge field and the SO(2) rotaion of N=2 spinor coordinates. The action is shown to satisfy the Gaillard-Zumino duality condition, which is a necessary and sufficient condition for a action to be self-dual. Our proof needs no gauge fixing for the $\kappa$-symmetry.