A multiple charged particle beam writing apparatus includes a defective pattern data generation circuitry configured to generate defective pattern data of a defective pattern having a shape of the defective region in the writing region; a reverse pattern data generation circuitry configured to generate reverse pattern data by reversing the defective pattern data; a combined-value pixel data generation circuitry configured to generate, for the each pixel, combined-value pixel data by adding a value defined in a reverse pattern pixel data and a value defined in a writing pattern pixel data; and a writing mechanism configured to perform multiple writing, using multiple charged particle beams, on the target object such that the each pixel is irradiated with a beam of a dose corresponding to a value defined in the combined-value pixel data.