A boot configured to be attached to a ferrule includes: a fiber insertion hole into which optical fibers are inserted; a lower part on one side with respect to the fiber insertion hole; and an upper part on another side with respect to the fiber insertion hole. The fiber insertion hole is disposed to correspond with fiber holes of the ferrule that are disposed in an array in one direction. The upper part includes a protrusion part that protrudes relative to an end surface of the lower part in a fiber insertion direction. The ferrule includes: an adhesive filling part configured to be filled with an adhesive; and a stepped part that guides the optical fibers into the fiber holes.