An optical fiber connection mechanism includes a pair of connectors and a split sleeve that are used in an endoscope. The connectors include respective ferrules, an end of a single-mode optical fiber and a collimator lens is mounted in each ferrule, and the collimator lens is disposed at the tip of the single-mode optical fiber. The optical fiber connection mechanism is configured so that when the ferrules are inserted into ends of the split sleeve, the collimator lenses face each other with a gap therebetween and the single-mode optical fibers are optically connected to each other. The ferrules are loosely fit in the corresponding connectors to be displaceable within a predetermined range in the direction along the optical axis of the single-mode optical fibers.