Ion cyclotron range of frequencies (ICRF) heating antennas in LHD are numerically simulated and analyzed by HFSS^TM finite-element electromagnetic wave field calculation code. The model includes an accurate vacuum chamber wall of LHD and ICRF antenna structure and a simple model of plasma in a helical configuration. Antenna coupling with plasma is simulated by an artificial freshwater volume with enhanced high permittivity of ε = 500-2000. RF current distribution and electromagnetic field distribution on and near the ICRF antenna are analyzed and well elucidated through a comparison with the experimental results. The frequency dependence of experimental loading resistance can be simulated by the calculation, and the RF dissipation on the antenna structure is studied and compared with experimental results. The local high heat load around gaps between the carbon side protectors is well explained, and the effect of gap distance is studied. Comparison with the experimental results reveals that the ICRF heating in the LHD, including the antenna and helical plasma, is well simulated by commercial HFSS^TM code analysis. It will also be useful for future improvements in ICRF antenna design in helical devices.