Millimeter wave imaging diagnostics such as electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) are advanced technology to investigate electron temperature/density profiles and their fluctuations in magnetically confined plasmas. We have installed an ECEI system in the large helical device (LHD) at National Institute for Fusion Science (NIFS). The optimization of a receiving antenna array is essential for the imaging diagnostics. We have designed and fabricated dual-dipole antenna array. In this paper, the design and fabrication process of dual-dipole antennas are described. The characterizations of the antennas are also reported by comparing simulation and experimental results.