Abstract: The present invention provides a novel use of a Maydis stigma extract in prophylaxis, alleviation, or therapy of sleep disorder. A Maydis stigma extract has the effect of reducing sleep onset latency and increasing sleep duration, as high as or higher than the effect of ketamine or pentobarbital, which are conventionally used as soporifics. As a natural substance, the Maydis stigma extract does not cause side effects, such as cytotoxicity, resistance, or dependency, even when used for a long term.