A charged particle beam writing apparatus includes an input unit configured to input writing data for writing a plurality of cell patterns including at least one cell pattern in which an identifier is added to each of data defining the at least one cell pattern extending over at least two small regions in a plurality of small regions obtained by virtually dividing a writing region, an extraction unit configured to extract the at least one cell pattern to which the identifier is added from the plurality of cell patterns, an output unit configured to output an error result when only one cell pattern is extracted, and a writing unit configured to write the plurality of cell patterns by irradiating a target workpiece with a charged particle beam, based on the writing data for which the error result is not output.