A beam writing apparatus includes a unit to obtain a specific value by calculating an integer by dividing a total irradiation time by a multiplied value of a region number and a repeating times number, and by multiplying the integer by the repeating times number, to add the repeating times number to the specific value when a region is in the multiple writing unit regions and is not a specific region and when a region number of the multiple writing unit region, defined excluding the specific region, is below or equal to a value obtained by dividing the total irradiation time by the multiplied value of the region number and the repeating times number, to obtain a first remainder, and dividing the first remainder by the repeating times number, and to treat an added value of the repeating times number and the specific value, as a total irradiation time.
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