A probe which allows optical fiber fixing tools to be distributed substantially uniformly and symmetrically longitudinally or laterally and is easily fitted, even when a head part size of a subject changes is provided. A plurality of optical fiber fixing tools which fix incident optical fibers and detection optical fibers are arranged on a fixing part in a substantially straight line shape, a plurality of the fixing parts are included, the fixing parts are arranged so that its straight line direction is oriented in a substantially parietal direction, the optical fiber fixing tool on the fixing part and the optical fiber fixing tool on the adjacent different fixing part are connected by a connecting member, and the connecting member is made rotatable around the optical fiber fixing tool, whereby the probe can be fitted so that the optical fibers are arranged substantially symmetrically and uniformly longitudinally or laterally.
