Provided are electron-emitting devices, electron sources, and image-forming apparatus improved in electron emission efficiency and in convergence of trajectories of emitted electrons. An electron-emitting device has a first electrode and a second electrode placed in opposition to each other with a gap between first and second electrodes on a surface of a substrate, and a plurality of fibers electrically connected to the first electrode and containing carbon as a main component, and the fibers are placed on a surface of the first electrode facing the second electrode.