Provided is a biological state assessment device for assessing biological state, such as mood or emotions, using non-invasive biophotonic measurement technology. The present invention includes a light irradiation unit (1041), a light-receiving unit (1061), and an inputting means (112). A subject (800) is presented with a plurality of different problems (first problem, second problem), and a biological signal in the interior of the subject is calculated from the intensity of light received by the light-receiving unit (1061). Subjective information about the subject is accepted by the inputting means (112). The difference is calculated between the subjective information and the relative value of the biological signal of the measurement point for the first problem and the biological signal of the measurement point for the second problem, and the result is displayed.