In one embodiment, a multi charged particle beam writing apparatus includes a blanking plate including a plurality of blankers, bitmap generation processing circuitry generating bitmap data for each writing pass of multi-pass writing, the bitmap data specifying irradiation time periods for a plurality of irradiation positions, a plurality of dose correction units configured to receive bitmap subdata items obtained by dividing the bitmap data from the bitmap generation processing circuitry, and correct the irradiation time periods to generate a plurality of dose data items corresponding to respective processing ranges, and data transfer processing circuitry transferring the plurality of dose data items to the blanking plate through a plurality of signal line groups. Each of the signal line groups corresponds to the blankers located in a predetermined region of the blanking plate. The data transfer processing circuitry changes the signal line groups, used to transfer the plurality of dose data items generated by the respective dose correction units, for each writing pass.