An optical fiber holding structure includes a light-transmitting tube configured to cover a surface-light-emitting optical fiber and a fixture configured to fix the tube to a building material. The tube is made of a material having such rigidity that the tube is not bent even when the tube is horizontally fixed by the fixture. The tube has a notch through which the optical fiber is introduced into the tube. The fixture includes an engaging portion, a mounting portion and a leg portion. The engaging portion is inserted into the tube through the notch to engage with an inner circumference of the tube. The mounting portion is mounted to the building material. The leg portion is configured to interconnect the engaging portion and the mounting portion with a predetermined gap left therebetween.