An electron beam length-measurement apparatus for measuring a length of a predetermined portion of an object by using an electron beam, includes: an electron gun for emitting the electron beam; a deflecting unit for deflecting the electron beam; an object holding unit on which the object is to be placed; a detector for detecting electrons that are scattered by the electron beam; a memory for storing layout position information that specifies a layout position at which the predetermined portion of the object; a length-measurement scanning controller for controlling the deflecting unit to scan with the electron beam to allow the layout position on the object to be irradiated with the electron beam; and a measurement unit operable to measure the length of the predetermined portion of the object based on a changing manner of the electrons successively detected by the detector while the length-measurement scanning controller scans with the electron beam.