In this study, we examined to difference in dietary protein contents on circadian rhythm of carbohydrate metabolism in the liver of rats. Blood sample were obtained at same time with a portal vein to the liver from the intestinal tract and a hepatic vein. From difference between blood glucose level in a portal vein and a hepatic vein, it was found that there was active gluconeogenesis in the fasting, especially in the group of high-protein diet. In fact, high-protein diet group was shift to the gluconeogenesis earlier than the other protein diet groups. The amplitude of the carbohydrate rhythm decreased with increase in dietary protein (casein) content. The plasma adiponectin involved in carbohydrate metabolism disappeared clear daily changes in all groups, but maintained elevated levels in rats fed low-protein diet. Therefore, it is clarified the effects of dietary protein intake on the various metabolic changes in the rats liver. From the perspective of the chrononutrition, we showed the importance of dietary protein intake for generation of the circadian rhythm of carbohydrate metabolism in the rats liver.