In this study, we deal with the tumbling, which is rotating motion with the axis perpendicular to the falling direction. Our purpose is to reveal the fundamental aerodynamic characteristics of the tumbling, experimentally. Regarding a test plate, we consider a prism with a rectangular cross section with a depth-to-width ratio λ of 0.3. The results are as follows. The reduced terminal rotating rate Ω^*, the lift coefficient C_L, the drag coefficient C_D and the lift-to-drag ratio C_L/C_D are independent of the aspect ratio AR, when AR is greater than 10. As the inertia momen ratio I^* increases from zero to 50, Ω^*, C_L and C_D increase. However, Ω^*, C_L and C_D become almost constant, at I^* greater than 50. We propose the empirical formulae to predict them. At low I^*, the tumbling shows a dominant periodicity of 360deg.