Circadian rhythm adjusting agents, clock gene expression cycle shortening agents, preventive or therapeutic agents and food and drink compositions for diseases caused by circadian rhythm disorder.

Problem to be solved. To provide a circadian rhythm adjusting agent derived from a plant belonging to the genus Zanthoxylum of the family Rutaceae, and to provide therapeutic agents and food and drink compositions and the like that contain the circadian rhythm adjusting agent. Solution. Provided is a circadian rhythm adjusting agent for shortening the circadian cycle, which contains as an active ingredient the extract of leaves, flowers, fruits, pericarps, barks, and trunks of a plant belonging to the genus Zanthoxylum of the family Rutaceae. The extract contains hydroxy-β-sanshool as an active ingredient and the circadian cycle is shortened by shortening the expression cycle of a clock gene. The circadian rhythm adjusting agent may be a food and drink composition for the prevention, alleviation, or treatment of sleep disorder or jet lag caused by circadian rhythm disturbances.