<p>Provided is a holder (60) which comprises at least two probe mount portions (61a) and is mounted to the head of a subject by inserting a light-transmitting probe (12) for applying light from the tip thereof or a light-receiving probe (13) for receiving light from the tip thereof in the probe mount portion (61a), the holder characterized by being provided with a linear backbone portion (62) extending in a first direction, at least two linear branch portions (61) extending in a second direction different from the first direction, and a disposition reference point (63a) disposed so as to match a first specific point, the first specific point being set in the head of the subject.</p>
