The present invention provides an optical element for measuring information of living body for noninvasively measuring a body fluid component in a test sample of living body with high accuracy, stability, and ease. The optical element includes a light incident surface, a contact surface contacting living body and having a groove to protrude living body and a light emission surface, in which a light incident from the light incident surface is applied to living body, and the light absorbed and scattered by living body is received and emitted from the light emission surface, a light transmittance controlling means is formed from the bottom part of the valley part of the groove, on at least a part of a wall surface of the light incident surface side and/or on a wall surface of the light emission surface side of the groove.