The brain state support apparatus 1 comprises a stimulus applying device 2, a light detecting device 3, a calculating section 13 for calculating the changed amount of total hemoglobin and the changed amount of oxygen saturation based on the light information, a determination section 14 for determining whether the brain state of the human body is in at least one of a relaxation mode, a concentration mode and an intermediate mode, based on the changed amount of total hemoglobin and the changed amount of oxygen saturation by applying a stimulus of an electrical signal having a predetermined frequency to the acupoint of the human body through the stimulus applying device 2; and a stimulus adjusting section 15 for adjusting a quantity of stimulus to be applied to an acupoint of the human body by the stimulus applying device 2.