In the present study, smoke-wire flow visualizations were conducted to investigate the flow structures generated by a tethered flight of a rhinoceros beetle in a wind tunnel. Measurements are done at five planes along the wing span while the varying the body angle (angle between the horizontal and the body axis)　and free-stream velocity to relate the advance ratio and Strouhal number which are widely accepted as important parameters on the aerodynamic force generation of flying insects. It is observed that the angle of wake-induced flow, spanwise flow in LEV (leading-edge vortex) and the instant of LEV generation vary depending on the body angles that represent different flight mode such as hovering, forward and take-off flights. On the other hand, it is found that most of aerodynamic forces would be generated by hindwings (flexible inner wings) compared to the elytra (hard outer wings) inferring from the size of the attached leading attached vortex (LEV) on the wings. Furthermore, specific flow patterns from other unsteady aerodynamic mechanisms such as clap-and-fling, wing-wing interaction and wake capture are found as well.