In order to precisely determine a stable measuring region appropriate for a measurement of biological information, and to measure a concentration of a specific component, i.e. biological information, without inconsistency, a biological information measuring device is provided with, a measuring region determining means for determining a measuring region in between an eponychium and a distal interphalangeal joint; an information detector for applying a light to measuring region; a light source for entering a light to information detector; a light detector for detecting a light which exits from the information detector; and a processor for measuring specific component based on information obtained from light detector.