In one embodiment, a charged particle beam writing apparatus includes a writer writing a pattern on a substrate placed on a stage by irradiating the substrate with a charged particle beam, a height detector detecting a surface height of a mark on the stage, an irradiation position detector detecting an irradiation position of the charged particle beam on the mark surface by irradiation with the charged particle beam focused at the surface height of the mark, a drift correction unit calculating an amount of drift of the charged particle beam on the mark surface from the irradiation position detected by the irradiation position detector, and generating correction information for correcting a shift in irradiation position caused by a drift on the substrate surface based on the amount of drift, and a writing control unit correcting the irradiation position of the charged particle beam by using the correction information.