[en] A tangential Fast-Ion D Alpha (FIDA) diagnostic is applied to the Large Helical Device (LHD) in order to observe energetic distribution of toroidal circulating energetic particles which are produced by tangential Negative Neutral Beams (NNB). A perpendicular Positive NB (PNB) is used as the diagnostic probe beam of the tangential-FIDA diagnostic in this observation geometry. In order to assess the appropriateness of the tangential-FIDA diagnostic, the experimental result was compared with a Silicon-diode-based Fast Neutral Analyzer (Si-FNA) which was installed on the same line of sight. As a result of the comparison, the tangential-FIDA and the Si-FNA experimental data obtained good linearity in the energy region from 60 keV to 180 keV. In addition, an enhanced FIDASIM was applied for analyzing the FIDA on the three-dimensional magnetic configuration fusion device. (author)