In order to investigate the effect of light-dark cycles on growth of Cassia nomame, plants were grown under 5 different light-dark cycles for 288 h that were 12h cycle (6L-6D), 18h cycle (9L-9D), 24 h cycle (12L-12D), 36 h cycle (18L-18D) and 48 h cycle (24L-24D) . The growth of plants under 24 h cycle was the best of all, those under 36 h cycle and 48 h cycle were the worst and those under 12 h cycle and 18 h cycle were medium. The leaves of C. nomame move under natural light-dark cycle, then we examined the leaf movement under the same light-dark cycles described above. The plants grown under 24 h cycle kept their regular and steady leaf movement, but ones under other cycles could not keep their regularity. It is natural to think that leaves moved under the control of endogenous rhythm and plants under light-dark cycles except 24 h had unsteady endogenous rhythms. These results suggest that the best condition of light-dark cycle for growth is one that helps plants keep their own endogenous rhythms.