We have developed an antireflecting plate with a novel structure to reduce the long-range fogging effect, which is especially serious in mask writing by a high acceleration voltage electron beam mask writing system. This structure is characterized by an array of holes whose axes converge to the beam irradiation position. These holes can efficiently absorb the electrons scattered at a reticle by avoiding the collision of the electrons with the inner walls. The reflectance of this structure is about 30% of that of the plane structure for 30 keV electrons, whereas that of a parallel hole array structure is about 40%. The fogging effect was evaluated in a high accelerating voltage (50 kV) electron beam mask writing system equipped with this new antireflecting plate, and nm-level global uniformity in pattern size was achieved.