Apparatus and method for modifying an object with electrons are provided, by which the object can be uniformly and efficiently modified with the electrons under a pressure substantially equal to atmospheric pressure even when having a relatively wide surface area to be treated. This method uses a cold-cathode electron emitter having the capability of emitting electrons from a planar electron emitting portion according to tunnel effect, and preferably comprising a pair of electrodes, and a strong field drift layer including nanocrystalline silicon disposed between the electrodes. The object is exposed to electrons emitted from the planar electron emitting portion by applying a voltage between the electrodes.