A multi charged particle beam writing method includes performing ON/OFF switching of a beam by an individual blanking system for the beam concerned, for each beam in multi-beams of charged particle beam, with respect to each time irradiation of irradiation of a plurality of times, by using a plurality of individual blanking systems that respectively perform beam ON/OFF control of a corresponding beam in the multi-beams, and performing blanking control, in addition to the performing ON/OFF switching of the beam for the each beam by the individual blanking system, with respect to the each time irradiation of the irradiation of the plurality of times, so that the beam is in an ON state during an irradiation time corresponding to irradiation concerned, by using a common blanking system that collectively performs beam ON/OFF control for a whole of the multi-beams.