For ultra-high speed recording, all-optical magnetic recording technology with circularly polarized lights has been studied [1-3]. However, it was difficult to localize circularly polarized light for realizing higher density magnetic recording because of the diffraction limit. Our proposed plasmonic cross antenna can generate the nano-sized circularly polarized light inside the recording media for high density magnetic recording [4, 5]. In this paper, we analyze the electromagnetic fields of a plasmonic cross antenna and the bit-patterned media by the ADE-FDTD method . The intensity of the electric fields inside the bit-patterned media and the speed to generate the circularly polarized light are discussed for all-optical magnetic recording.