A probe (10； 11) includes: light emitting (210) and receiving (220) sections； an attachment band (110； 111) including a first surface facing the living tissue and a second surface opposite to the first surface, a part of the first surface in which one of a hook portion (116) and a loop portion (115) is provided, a part of the second surface in which the other is provided, the attachment band (110； 111) to be wrapped around the living tissue to engage the hook (116) and loop (115) portions with each other； and a compressible member (150) attached to the first surface, being in contact with the living tissue when the attachment band (110； 111) is attached to the living tissue, the compressible member (150) which is larger in width than the attachment band (110； 111) and ends of which extend beyond ends of the attachment band (110； 111).
