We consider optimal beamforming (BF) for the multiantenna full-duplex (FD) amplify-and-forward relay that maximizes the secrecy rate in the relay eavesdropper channel. We first show that zero forcing condition (ZFC) with no self-interference from the loop-back channel at the FD relay is the necessary condition for finding the optimal beamformer. Then, we provide an optimization method to locate the best pair among the ZFC beamformers. Through some simulations, we evaluate and compare the performances of the proposed optimal zero forcing BF scheme and a reference BF scheme.