The purpose of this study was to clarify effects of foot bath at 42°C for 10 min on cerebral circulation and mental function in elderly persons. The subjects of this study were 12 elderly persons (average 83.1 years old). Tissue hemoglobin concentration and blood flow at the cerebral frontal cortex were measured using near-infrared spectroscopy and blood pressure and heart rate using an autonomic spygmomanometer during for each 10 minutes before foot bath, during foot bath, and after foot bath. We measured subject's arithmetic speed and mistaken numbers as mental function. During foot bath the blood flow and after foot bath oxyhemoglobin at frontal cortex were significantly increased. Heart rate was significant increased after foot bath. But deoxyhemoglobin and blood pressure did not changed during foot bath. In addition to arithmetic speed and mistaken numbers were same before and after foot bath. These findings suggest that cerebral circulation is changed by foot bath, but mental functions is not before and after foot bath.