In one embodiment, a first storage storing writing data, a second storage storing correction data for correcting an error in a writing position due to factors including bending of the substrate, a cell data allocator virtually dividing a writing region of the substrate into blocks, and allocating a cell to the blocks in consideration of the correction data, a plurality of bitmap data generators virtually dividing the blocks into meshes, calculating an irradiation amount per mesh region, and generating bitmap data which assigns the irradiation amount to each mesh region, and a shot data generator generating shot data that defines an irradiation time for each beam. The cell data allocator virtually divides the writing region by division lines in a direction different from a writing forward direction to generate a plurality of division regions. The plurality of bitmap data generators generate pieces of bitmap data of the different division regions.