A charged particle beam writing apparatus includes an area density calculation unit to calculate a pattern area density weighted using a dose modulation value, which has previously been input from an outside and in which an amount of correction of a dimension variation due to a proximity effect has been included, a fogging correction dose coefficient calculation unit to calculate a fogging correction dose coefficient for correcting a dimension variation due to a fogging effect by using the pattern area density weighted using the dose modulation value having been input from the outside, a dose calculation unit to calculates a dose of a charged particle beam by using the fogging correction dose coefficient and the dose modulation value, and a writing unit to write a pattern on a target object with the charged particle beam of the dose.